Microelectronic circuits by Sedra Smith,5th ed readable

Con­sider the amplifier of Example 1.2 with a positive input signal of 1 mV superimposed on the dc bias voltage V',.. b The BJT connected as an amplifier with the emitter as a common ter

THE OXFORD SERIES IN ELECTRICAL AND COMPUTER

ENGINEERING

A d e l S S e d r a , Series E d i t o r

A l l e n a n d H o l b e r g , CMOS Analog Circuit Design, 2nd Edition

B o b r o w , Elementary Linear Circuit Analysis, 2nd Edition

B o b r o w , Fundamentals of Electrical Engineering, 2nd Edition

B u r n s a n d R o b e r t s , An Introduction to Mixed-Signal IC Test and Measurement

C a m p b e l l , The Science and Engineering of Microelectronic Fabrication, 2nd Edition

C h e n , Digital Signal Processing

C h e n , Linear System Theory and Design, 3rd Edition

C h e n , Signals and Systems, 3rd Edition

C o m e r , Digital Logic and State Machine Design, 3rd Edition

C o m e r , Microprocessor-based System Design

C o o p e r a n d M c G i l l e m , Probabilistic Methods of Signal and System Analysis, 3rd Edition

D e C a r l o a n d L i n , Linear Circuit Analysis, 2nd Edition

Dimitrijev, Understanding Semiconductor Devices

Fortney, Principles of Electronics: Analog & Digital

F r a n c o , Electric Circuits Fundamentals

G h a u s i , Electronic Devices and Circuits: Discrete and Integrated

G u r u a n d H i z i r o g l u , Electric Machinery and Transformers, 3rd Edition

H o u t s , Signal Analysis in Linear Systems

J o n e s , Introduction to Optical Fiber Communication Systems

K r e i n , Elements of Power Electronics

K u o , Digital Control Systems, 3rd Edition

L a t h i , Linear Systems and Signals, 2nd Edition

L a t h i , Modern Digital and Analog Communications Systems, 3rd Edition

L a t h i , Signal Processing and Linear Systems

M a r t i n , Digital Integrated Circuit Design

M i n e r , Lines and Electromagnetic Fields for Engineers

P a r h a m i , Computer Arithmetic

R o b e r t s a n d S e d r a , SPICE, 2nd Edition

R o u l s t o n , An Introduction to the Physics of Semiconductor Devices

S a d i k u , Elements of Electromagnetics, 3rd Edition

S a n t i n a , S t u b b e m d , a n d Hostetter, Digital Control System Design, 2nd Edition

S a r m a , Introduction to Electrical Engineering

S c h a u m a n n a n d Van V a l k e n b u r g , Design of Analog Filters

S c h w a r z a n d O l d h a m , Electrical Engineering: An Introduction, 2nd Edition

S e d r a a n d S m i t h , Microelectronic Circuits, 5th Edition

Stefani, Savant, S h a h i a n , a n d Hostetter, Design of Feedback Control Systems, 4th Edition

T s i v i d i s , Operation and Modeling of the MOS Transistor, 2nd Edition

Van V a l k e n b u r g , Analog Filter Design

W a r n e r a n d G r u n g , Semiconductor Device Electronics

W o l o v i c h , Automatic Control Systems

Yariv, Optical Electronics in Modern Communications, 5th Edition

Zak, Systems and Control

H E D I T I O N

MICROELECTRONIC CIRCUITS

Oxford University Press

Oxford New York

Auckland Bangkok Buenos Aires Cape Town Chennai

Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata

Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi

São Paulo Shanghai Taipei Tokyo Toronto

Copyright © 1982, 1987, 1991, 1998, 2004 by Oxford University Press, Inc

Published by Oxford University Press, Inc

198 Madison Avenue, New York, New York 10016

www.oup.com

Oxford is a registered trademark of Oxford University Press

All rights reserved No part of this publication may be reproduced,

stored in a retrieval system, or transmitted, in any form or by any means,

electronic, mechanical, photocopying, recording, or otherwise,

without the prior permission of Oxford University Press

ISBN 0-19-514252-7

Cover Illustration: The chip shown is an inside view of a mass-produced surface-micromachined gyroscope

sys-tem, integrated on a 3mm by 3mm die, and using a standard 3-m 2-V BiCMOS process suited for the harsh

auto-motive environment This first single-chip gyroscopic sensor, in which micro-mechanical and electronic

components are intimately entwined on the same chip, provides unprecedented performance through the use of a

collection of precision-directed techniques, including emphasis on differential operation (both mechanically and

electronically) bolstered by trimmable thin-film resistive components This tiny, robust, low-power,

angular-rate-to-voltage transducer, having a sensitivity of 12.5mV/7s and resolution of 0.0157s (or 507hour) has a myriad of

applications—including automotive skid control and rollover detection, dead reckoning for GPS backup and robot

motion control, and camera-field stabilization The complete gyroscope package, weighing 1/3 gram with a

vol-ume of 1/6 cubic centimeter, uses 30mW from a 5-V supply Source: John A Geen, Steven J Sherman, John F

Chang, Stephen R Lewis; Single-chip surface micromachined integrated Gyroscope with 50°/h Allan deviation,

IEEE Journal of Solid-State Circuits, vol 37, pp 1860-1866, December 2002 (Originally presented at ISSCC

2002.) Photographed by John Chang, provided by John Geen, both of Analog Devices, Micromachine Products

Division, Cambridge, MA, USA

A N A L O G A N D D I G I T A L I N T E G R A T E D

PART III S E L E C T E D T O P I C S 1010

A P P E N D I X E S

A VLSI Fabrication Technology A-1

B Two-Port Network Parameters B-1

C S o m e Useful Network Theorems C-1

D Single-Time-Constant Circuits D-1

E s-Domain Analysis: Poles, Zeros, and B o d e Plots E-1

F Bibliography F-1

G Standard Resistance Values and Unit Prefixes G-1

H Answers to Selected Problems H-1

I N D E X IN-1

1.4.8 Nonlinear Transfer Characteristics and Biasing 19

1.4.9 Symbol Convention 2 2

1.5 C i r c u i t M o d e l s for A m p l i f i e r s 23

1.5.1 Voltage Amplifiers 2 3

1.5.2 Cascaded Amplifiers 25

1.5.3 Other Amplifier Types 2 7

1.5.4 Relationships Between the Four Amplifier Models 2 7

1.7.4 The Ideal VTC 43 1.7.5 Inverter Implementation 43

2.1.2 Function and Characteristics of the Ideal

Op Amp 65

2.1.3 Differential and Common-Mode Signals 6 7

2.2 T h e I n v e r t i n g C o n f i g u r a t i o n 68 2.2.1 The Closed-Loop Gain 69 2.2.2 Effect of Finite Open-Loop Gain 71

2.2.3 Input arid Output Resistances 72

2.2.4 An Important Application—The Weighted Summer 75

2.3 T h e N o n i n v e r t i n g C o n f i g u r a t i o n 7 7

2.3.1 The Closed-Loop Gain 77

2.3.2 Characteristics of the Noninverting

Configuration 78 2.3.3 Effect of Finite Open-Loop Gain 78 2.3.4 The Voltage Follower 79

2.4 Difference A m p l i f i e r s 81 2.4.1 A Single Op-Amp Difference Amplifier 82 2.4.2 A Superior Circuit—The Instrumentation Amplifier 85 2.5 Effect of Finite O p e n - L o o p G a i n a n d B a n d w i d t h o n

C i r c u i t P e r f o r m a n c e 89 2.5.1 Frequency Dependence of the Open-Loop Gain 89 2.5.2 Frequency Response of Closed-Loop Amplifiers 91 2.6 L a r g e - S i g n a l O p e r a t i o n of O p A m p s 94

2.6.1 Output Voltage Saturation 94 2.6.2 Output Current Limits 94 2.6.3 Slew Rate 95

2.6.4 Full-Power Bandwidth 97 2.7 D C I m p e r f e c t i o n s 98

2.7.1 Offset Voltage 98 2.7.2 Input Bias and Offset Currents 102 2.8 I n t e g r a t o r s a n d Differentiators 105 2.8.1 The Inverting Configuration with General Impedances 105 2.8.2 The Inverting Integrator 107

2.8.3 The Op-Amp Differentiator 112 2.9 T h e S P I C E O p - A m p M o d e l a n d S i m u l a t i o n E x a m p l e s 114 2.9.1 Linear Macromodel 115

D E T A I L E D T A B L E O F C O N T E N T S

I n t r o d u c t i o n 235 4.1 D e v i c e S t r u c t u r e a n d P h y s i c a l O p e r a t i o n 236 4.1.1 Device Structure 236

4.1.2 Operation with No Gate Voltage 238 4.1.3 Creating a Channel for Current Flow 238

4.2.2 The i D -v DS Characteristics 249 4.2.3 Finite Output Resistance in Saturation 253 4.2.4 Characteristics of the p-Channel MOSFET 256 4.2.5 The Role of the Substrate—The Body Effect 258 4.2.6 Temperature Effects 259

4.2.7 Breakdown and Input Protection 259 4.2.8 Summary 260

4.3 M O S F E T Circuits at D C 262 4.4 T h e M O S F E T as a n A m p l i f i e r a n d as a S w i t c h 270

4.4.1 Large-Signal Operation—The Transfer Characteristic 2 7 1

4.4.2 Graphical Derivation of the Transfer Characteristic 273 4.4.3 Operation as a Switch 274

4.4.4 Operation as a Linear Amplifier 274

4.4.5 Analytical Expressions for the Transfer Characteristic 2 7 5

4.4.6 A Final Remark on Biasing 280 4.5 B i a s i n g in M O S A m p l i f i e r Circuits 280 4.5.1 Biasing by Fixing V GS 280 4.5.2 Biasing by Fixing V G and Connecting a Resistance

in the Source 281 4.5.3 Biasing Using a Drain-to-Gate Feedback Resistor 284 4.5.4 Biasing Using a Constant-Current Source 285 4.5.5 A Final Remark 287

4 6 S m a l l - S i g n a l O p e r a t i o n a n d M o d e l s 287 4.6.1 The DC Bias Point 287

4.6.2 The Signal Current in the Drain Terminal 288 4.6.3 The Voltage Gain 289

4.6.4 Separating the DC Analysis and the Signal Analysis 290 4.6.5 Small-Signal Equivalent-Circuit Models 290

4.6.6 The Transconductance g m 292

4.6.7 The T Equivalent-Circuit Model 2 9 5

4.6.8 Modeling the Body Effect 296 4.6.9 Summary 297

4.7 S i n g l e - S t a g e M O S A m p l i f i e r s 299 4.1.1 The Basic Structure 299 4.7.2 Characterizing Amplifiers 301 4.7.3 The Common-Source (CS) Amplifier 306 4.7.4 The Common-Source Amplifier with a Source Resistance 309

3.2 T e r m i n a l C h a r a c t e r i s t i c s of J u n c t i o n D i o d e s 147 3.2.1 The Forward-Bias Region 148

3.2.2 The Reverse-Bias Region 152 3.2.3 The Breakdown Region 152 3.3 M o d e l i n g t h e D i o d e F o r w a r d C h a r a c t e r i s t i c 153 3.3.1 The Exponential Model 153

3.3.2 Graphical Analysis Using the Exponential Model 154 3.3.3 Iterative Analysis Using the Exponential Model 154 3.3.4 The Need for Rapid Analysis 155

3.3.5 The Piecewise-Linear Model 755

3.3.6 The Constant-Voltage-Drop Model 157 3.3.7 The Ideal-Diode Model 158

3.3.8 The Small-Signal Model 159

3.3.9 Use of the Diode Forward Drop in

Voltage Regulation 163 3.3.10 Summary 165

3.4 O p e r a t i o n in t h e R e v e r s e B r e a k d o w n R e g i o n —

Z e n e r D i o d e s 167 3.4.1 Specifying and Modeling the Zener Diode 167 3.4.2 Use of the Zener as a Shunt Regulator 168 3.4.3 Temperature Effects 170

3.4.4 A Final Remark 171 3.5 Rectifier Circuits 171 3.5.1 The Half-Wave Rectifier 172 3.5.2 The Full-Wave Rectifier 174 3.5.3 The Bridge Rectifier 176

3.5.4 The Rectifier with a Filter Capacitor—

The Peak Rectifier 177

3.5.5 Precision Half-Wave Rectifier—

The Super Diode 183 3.6 L i m i t i n g a n d C l a m p i n g C i r c u i t s 184 3.6.1 Limiter Circuits 184

3.6.2 The Clamped Capacitor or DC Restorer 187 3.6.3 The Voltage Doubler 189

3.7 P h y s i c a l O p e r a t i o n of D i o d e s 190 3.7.1 Basic Semiconductor Concepts 190 3.7.2 T h e p n Junction Under Open-Circuit Conditions 196 3.7.3 The pn Junction Under Reverse-Bias Conditions 199 3.7.4 T h e J u n c t i o n in the Breakdown Region 203

3.7.5 The pn Junction Under Forward-Bias

Conditions 204 3.7.6 Summary 208 3.8 S p e c i a l D i o d e T y p e s 209 3.8.1 The Schottky-Barrier Diode (SBD) 210 3.8.2 Varactors 210

3.8.3 Photodiodes 210 3.8.4 Light-Emitting Diodes (LEDs) 211 3.9 T h e S P I C E D i o d e M o d e l a n d S i m u l a t i o n E x a m p l e s 212 3.9.1 The Diode Model 212

3.9.2 The Zener Diode Model 2 1 3

S u m m a r y 217

P r o b l e m s 218

5.6.7 The T Model 449 5.6.8 Application of the Small-Signal Equivalent Circuits 450

5.6.9 Performing Small-Signal Analysis Directly on the

Circuit Diagram 457

5.6.10 Augmenting the Small-Signal Models to Account

for the Early Effect 457 5.6.11 Summary 458 5.7 S i n g l e - S t a g e B J T A m p l i f i e r s 460 5.7.1 The Basic Structure 460 5.7.2 Characterizing BJT Amplifiers 461 5.7.3 The Common-Emitter (CE) Amplifier 467

5.7.4 The Common-Emitter Amplifier with an Emitter

Resistance 470 5.7.5 The Common-Base (CB) Amplifier 475

5.7.6 The Common-Collector (CC) Amplifier or

Emitter Follower 478 5.7.7 Summary and Comparisons 483 5.8 T h e B J T Internal Capacitances and H i g h - F r e q u e n c y M o d e l 485

5.8.1 The Base-Charging or Diffusion Capacitance C de 486

5.8.2 The Base-Emitter Junction Capacitance C je 486

5.8.3 The Collector-Base Junction Capacitance Cu 487 5.8.4 The High-Frequency Hybrid-^ Model 487 5.8.5 The Cutoff Frequency 487

5.8.6 Summary 490 5.9 F r e q u e n c y R e s p o n s e of t h e C o m m o n - E m i t t e r A m p l i f i e r 491

5.9.1 The Three Frequency Bands 491 5.9.2 The High-Frequency Response 492 5.9.3 The Low-Frequency Response 497 5.9.4 A Final Remark 503

5.10 T h e B a s i c B J T D i g i t a l L o g i c I n v e r t e r 503

5.10.1 The Voltage Transfer Characteristic 504 5.10.2 Saturated Versus Nonsaturated BJT Digital Circuits 505 5.11 T h e S P I C E B J T M o d e l a n d S i m u l a t i o n E x a m p l e s 507

5.11.1 The SPICE Ebers-Moll Model of the BJT 507 5.11.2 The SPICE Gummel-Poon Model of the BJT 509 5.11.3 The SPICE BJT Model Parameters 510

5.11.4 The BJT Model Parameters BF and BR in SPICE 510

4.7.5 The Common-Gate (CG) Amplifier 311 4.7.6 The Common-Drain or Source-Follower Amplifier 315 4.7.7 Summary and Comparisons 318

4.8 T h e M O S F E T Internal C a p a c i t a n c e s and H i g h - F r e q u e n c y M o d e l 320 4.8.1 The Gate Capacitive Effect 321

4.8.2 The Junction Capacitances 322 4.8.3 The High-Frequency MOSFET Model 322 4.8.4 The MOSFET Unity-Gain Frequency (f T ) 324 4.8.5 Summary 325

4.9 F r e q u e n c y R e s p o n s e of the C S A m p l i f i e r 326 4.9.1 The Three Frequency Bands 326 4.9.2 The High-Frequency Response 328 4.9.3 The Low-Frequency Response 332 4.9.4 A Final Remark 336

4 1 0 T h e C M O S D i g i t a l L o g i c I n v e r t e r 336

4.10.1 Circuit Operation 337 4.10.2 The Voltage Transfer Characteristic 339 4.10.3 Dynamic Operation 342

4.10.4 Current Flow and Power Dissipation 345 4.10.5 Summary 346

4 1 1 T h e D e p l e t i o n - T y p e M O S F E T 346

4 1 2 T h e S P I C E M O S F E T M o d e l a n d S i m u l a t i o n E x a m p l e 351 A.U.I MOSFET Models 351

4.12.2 MOSFET Model Parameters 352

S u m m a r y 359

P r o b l e m s 360

I n t r o d u c t i o n 377 5.1 D e v i c e S t r u c t u r e a n d P h y s i c a l O p e r a t i o n 378 5.1.1 Simplified Structure and Modes of Operation 378 5.1.2 Operation of the npn Transistor in the Active Mode 380 5.1.3 Structure of Actual Transistors 386

5.1.4 The Ebers-Moll (EM) Model 387 5.1.5 Operation in the Saturation Mode 390 5.1.6 The pnp Transistor 391

5.2 C u r r e n t - V o l t a g e C h a r a c t e r i s t i c s 392 5.2.1 Circuit Symbols and Conventions 392 5.2.2 Graphical Representation of Transistor Characteristics 397

5.2.3 Dependence of i c on the Collector Voltage—The Early

Effect 399 5.2.4 The Common-Emitter Characteristics 401 5.2.5 Transistor Breakdown 406

5.2.6 Summary 407 5.3 T h e B J T as an A m p l i f i e r a n d as a S w i t c h 407 5.3.1 Large-Signal Operation—The Transfer Characteristic 410 5.3.2 Amplifier Gain 412

5.3.3 Graphical Analysis 415 5.3.4 Operation as a Switch 419 5.4 B J T Circuits at D C 421

6.2.4 Combining MOS and Bipolar Transistors—BiCMOS Circuits 567

6.2.5 Validity of the Square-Law MOSFET Model 562

6.3 I C B i a s i n g — C u r r e n t S o u r c e s , C u r r e n t M i r r o r s , a n d

C u r r e n t - S t e e r i n g Circuits 562 6.3.1 The Basic MOSFET Current Source 562 6.3.2 MOS Current-Steering Circuits 565 6.3.3 BJT Circuits '567

6.4 H i g h - F r e q u e n c y R e s p o n s e — G e n e r a l C o n s i d e r a t i o n s 571 6.4.1 The High-Frequency Gain Function 572

6.4.2 Determining the 3-dB Frequency f H 573

6.4.3 Using Open-Circuit Time Constants for the Approximate

Determination off H 575 6.4.4 Miller's Theorem 578

6.5 T h e C o m m o n - S o u r c e a n d C o m m o n - E m i t t e r A m p l i f i e r s w i t h A c t i v e

L o a d s 582 6.5.1 The Common-Source Circuit 582 6.5.2 CMOS Implementation of the Common-Source Amplifier 583 6.5.3 The Common-Emitter Circuit 588

6.6 H i g h - F r e q u e n c y R e s p o n s e of t h e C S a n d C E A m p l i f i e r s 588 6.6.1 Analysis Using Miller's Theorem 589

6.6.2 Analysis Using Open-Circuit Time Constants 590

6.6.3 Exact Analysis 597

6.6.4 Adapting the Formulas for the Case of the CE Amplifier 595

6.6.5 The Situation When R sig Is Low 597

6.7 T h e C o m m o n - G a t e a n d C o m m o n - B a s e A m p l i f i e r s w i t h

A c t i v e L o a d s 600 6.7.1 The Common-Gate Amplifier 600 6.7.2 The Common-Base Amplifier 610 6.7.3 A Concluding Remark 613 6.8 T h e C a s c o d e A m p l i f i e r 613 6.8.1 The MOS Cascode 614 6.8.2 Frequency Response of the MOS Cascode 618 6.8.3 The BJT Cascode 623

6.8.4 A Cascode Current Source 625 6.8.5 Double Cascoding 626 6.8.6 The Folded Cascode 627 6.8.7 BiCMOS Cascodes 628

D E T A I L E D T A B L E O F C O N T E N T S „ x i i i

I n t r o d u c t i o n 687 7.1 T h e M O S Differential P a i r 688

7.1.1 Operation with a Common-Mode Input

Voltage 689

7.1.2 Operation with a Differential Input Voltage 697

7.1.3 Large-Signal Operation 693 7.2 S m a l l - S i g n a l O p e r a t i o n of t h e M O S Differential P a i r 696 7.2.1 Differential Gain 697

7.2.2 Common-Mode Gain and Common-Mode Rejection Ratio

(CMRR) 700 7.3 T h e B J T Differential Pair 704 7.3.1 Basic Operation 704 7.3.2 Large-Signal Operation 707 7.3.3 Small-Signal Operation 709

7.4 O t h e r N o n i d e a l Characteristics of the Differential

Amplifier 720 7.4 l' Input Offset Voltage of the MOS Differential Pair 720

7.4.2 Input Offset Voltage of the Bipolar Differential Pair 723

7.4.3 Input Bias and Offset Currents of the Bipolar Pair 725 1AA Input Common-Mode Range 726

7.4.5 A Concluding Remark 726 7.5 T h e Differential A m p l i f i e r w i t h A c t i v e L o a d 727 7.5.1 Differential-to-Single-Ended Conversion 727 • 7.5.2 The Active-Loaded MOS Differential Pair 728

7.5.3 Differential Gain of the Active-Loaded

MOS Pair 729

7.5.5 The Bipolar Differential Pair with Active Load 733

6.9 T h e C S a n d C E A m p l i f i e r s w i t h S o u r c e ( E m i t t e r ) D e g e n e r a t i o n 629 6.9.1 The CS Amplifier with a Source Resistance 629

6.9.2 The CE Amplifier with an Emitter Resistance 633 6.10 T h e S o u r c e and E m i t t e r F o l l o w e r s 635

6.10.1 The Source Follower 635 6.10.2 Frequency Response of the Source Follower 637 6.10.3 The Emitter Follower 639

6.11 S o m e Useful T r a n s i s t o r P a i r i n g s 641 6.11.1 The C D - C S , C C - C E and C D - C E Configurations 641 6.11.2 The Darlington Configuration 645

6.11.3 The C C - C B and C D - C G Configurations 646

6.12 C u r r e n t - M i r r o r C i r c u i t s with I m p r o v e d

P e r f o r m a n c e 649 6.12.1 Cascode MOS Mirrors 649 6.12.2 A Bipolar Mirror with Base-Current Compensation 650

6.12.3 The Wilson Current Mirror 657

6.12.4 The Wilson MOS Mirror 652 6.12.5 The Widlar Current Source 653 6.13 S P I C E S i m u l a t i o n E x a m p l e s 656

S u m m a r y 665

P r o b l e m s 666

X l v D E T A I L E D T A B L E O F C O N T E N T S

8.10 Stability S t u d y U s i n g B o d e P l o t s 845

8.10.1 Gain and Phase Margins 845 8.10.2 Effect of Phase Margin on Closed-Loop Response 846 8.10.3 An Alternative Approach for Investigating Stability 847 8.11 F r e q u e n c y C o m p e n s a t i o n 849

8.11.1 Theory 850 8.11.2 Implementation 851 8.11.3 Miller Compensation and Pole Splitting 852 8.12 S P I C E S i m u l a t i o n E x a m p l e 855

S u m m a r y 859

P r o b l e m s 860

I n t r o d u c t i o n 871 9.1 T h e T w o - S t a g e C M O S O p A m p 872 9.1.1 The Circuit 872

9.1.2 Input Common-Mode Range and Output Swing 873

9.1.4 Frequency Response 876 9.1.5 Slew Rate 879

9.2 T h e F o l d e d - C a s c o d e C M O S O p A m p 883 9.2.1 The Circuit 883

9.2.2 Input Common-Mode Range and the Output Voltage Swing 885

9.2.3 Voltage Gain 886 9.2.4 Frequency Response 888 9.2.5 Slew Rate 888

9.2.6 Increasing the Input Common-Mode Range:

Rail-to-Rail Input Operation 890

9.2.7 Increasing the Output Voltage Range:

The Wide-Swing Current Mirror 892 9.3 T h e 7 4 1 O p - A m p C i r c u i t 893

9.3.1 Bias Circuit 893 9.3.2 Short-Circuit Protection Circuitry 895 9.3.3 The Input Stage 895

9.3.4 The Second Stage 895 9.3.5 The Output Stage 896 9.3.6 Device Parameters 898 9.4 D C A n a l y s i s of t h e 7 4 1 899 9.4.1 Reference Bias Current 899 9.4.2 Input-Stage Bias 899 9.4.3 Input Bias and Offset Currents 902 9.4.4 Input Offset Voltage 902

9.4.5 Input Common-Mode Range 902 9.4.6 Second-Stage Bias 902

9.4.7 Output-Stage Bias 903 9.4.8 Summary 904 9.5 S m a l l - S i g n a l A n a l y s i s of t h e 7 4 1 905 9.5.1 The Input Stage 905

9.5.2 The Second Stage 910 9.5.3 The Output Stage 912

7.6 F r e q u e n c y R e s p o n s e of t h e Differential A m p l i f i e r 740 7.6.1 Analysis of the Resistively Loaded MOS Amplifier 740 7.6.2 Analysis of the Active-Loaded MOS Amplifier 744 7.7 M u l t i s t a g e A m p l i f i e r s 749

1.1.1 A Two-Stage CMOS Op Amp 749 1.1.2 A Bipolar Op Amp 758

8.2.2 Bandwidth Extension 795 8.2.3 Noise Reduction 796 8.2.4 Reduction in Nonlinear Distortion 797 8.3 T h e F o u r B a s i c F e e d b a c k T o p o l o g i e s 798 8.3.1 Voltage Amplifiers 799

8.3.2 Current Amplifiers 799 8.3.3 Transconductance Amplifiers 801 8.3.4 Transresistance Amplifiers 802 8.4 T h e S e r i e s - S h u n t F e e d b a c k A m p l i f i e r 802 8.4.1 The Ideal Situation 802

8.4.2 The Practical Situation 804 8.4.3 Summary 807

8.5 T h e S e r i e s - S e r i e s F e e d b a c k A m p l i f i e r 811 8.5.1 The Ideal Case 811

8.5.2 The Practical Case 812 8.5.3 Summary 814

8.6 T h e S h u n t - S h u n t a n d S h u n t - S e r i e s F e e d b a c k

A m p l i f i e r s 818 8.6.1 The Shunt-Shunt Configuration 819 8.6.2 An Important Note 823

8.6.3 The Shunt-Series Configuration 823 8.6.4 Summary of Results 831

8.7 D e t e r m i n i n g t h e L o o p G a i n 831 8.7.1 An Alternative Approach for Finding A/5 831

8.7.2 Equivalence of Circuits from a Feedback-Loop

Point of View 833 8.8 T h e Stability P r o b l e m 834 8.8.1 Transfer Function of the Feedback Amplifier 834 8.8.2 The Nyquist Plot 835

8.9 Effect of F e e d b a c k on t h e A m p l i f i e r P o l e s 836 8.9.1 Stability and Pole Location 837

8.9.2 Poles of the Feedback Amplifier 838 8.9.3 Amplifier with Single-Pole Response 838 8.9.4 Amplifier with Two-Pole Response 839 8.9.5 Amplifiers with Three or More Poles 843

x v i

9.6 G a i n , F r e q u e n c y R e s p o n s e , a n d S l e w R a t e of t h e 7 4 1 917 9.6.1 Small-Signal Gain 917

9.6.2 Frequency Response 917 9.6.3 A Simplified Model 918 9.6.4 Slew Rate 919

9.6.5 Relationship Between/, and SR 920 9.7 D a t a C o n v e r t e r s — A n I n t r o d u c t i o n 922 9.7.1 Digital Processing of Signals 922 9.7.2 Sampling of Analog Signals 922 9.7.3 Signal Quantization 924 9.1 A The AID and D/A Converters as Functional Blocks 924 9.8 D / A C o n v e r t e r C i r c u i t s 925

9.8.1 Basic Circuit Using Binary-Weighted Resistors 925

9.8.2 R-2R Ladders 926

9.8.3 A Practical Circuit Implementation 9 2 7

9.8.4 Current Switches 928 9.9 A / D C o n v e r t e r Circuits 929

9.9.1 The Feedback-Type Converter 929 9.9.2 The Dual-Slope A/D Converter 930 9.9.3 The Parallel or Flash Converter 932 9.9.4 The Charge-Redistribution Converter 932

10.1.1 Digital IC Technologies and Logic-Circuit Families 950 10.1.2 Logic-Circuit Characterization 952

10.1.3 Styles for Digital System Design 954

10.1.4 Design Abstraction and Computer Aids 9 5 5

10.2 D e s i g n a n d P e r f o r m a n c e A n a l y s i s of t h e C M O S I n v e r t e r 955 10.2.1 Circuit Structure 955

10.2.2 Static Operation 956 10.2.3 Dynamic Operation 958 10.2.4 Dynamic Power Dissipation 961 10.3 C M O S L o g i c - G a t e C i r c u i t s 963

10.3.1 Basic Structure 963 10.3.2 The Two-Input NOR Gate 966 10.3.3 The Two-Input NAND Gate 966 10.3.4 A Complex Gate 967

10.3.5 Obtaining the PUN from the PDN and Vice Versa 968 10.3.6 The Exclusive-OR Function 969

10.3.7 Summary of the Synthesis Method 970 10.3.8 Transistor Sizing 970

10.3.9 Effects of Fan-In and Fan-Out on Propagation Delay 973

10.4 P s e u d o - N M O S L o g i c C i r c u i t s 974 10.4.1 The Pseudo-NMOS Inverter 974

10.4.2 Static Characteristics 975

D E T A I L E D T A B L E O F C O N T E N T S '

10.4.3 Derivation of the VTC 976 10.4.4 Dynamic Operation 979

10.4.5 Design 979 10.4.6 Gate Circuits 980

10.4.7 Concluding Remarks 9S0

10.5 P a s s - T r a n s i s t o r L o g i c C i r c u i t s 982 10.5.1 An Essential Design Requirement 983 10.5.2 Operation with NMOS Transistors as Switches 984 10.5.3 The Use of CMOS Transmission Gates as Switches 988 10.5.4 Pass-Transistor Logic Circuit Examples 990

10.5.5 A Final Remark 991 10.6 D y n a m i c L o g i c C i r c u i t s 991

10.6.1 Basic Principle 992 10.6.2 Nonideal Effects 993 10.6.3 Domino CMOS Logic 996

11.1.4 A Simpler CMOS Implementation of the Clocked SR

Flip-Flop 1019 11.1.5 D Flip-Flop Circuits 1019 11.2 M u l t i v i b r a t o r Circuits 1021

11.2.1 A CMOS Monostable Circuit 1022 11.2.2 An Astable Circuit 1026

11.2.3 The Ring Ospillator 1027 11.3 S e m i c o n d u c t o r M e m o r i e s : T y p e s and A r c h i t e c t u r e s 1028

11.3.1 Memory-Chip Organization 1028 11.3.2 Memory-Chip Timing 1030 11.4 R a n d o m - A c c e s s M e m o r y ( R A M ) C e l l s 1031 11.4.1 Static Memory Cell 1031

11.4.2 Dynamic Memory Cell 1036 11.5 S e n s e A m p l i f i e r s a n d A d d r e s s D e c o d e r s ~ 1038

11.5.1 The Sense Amplifier 1038 11.5.2 The Row-Address Decoder 1043 11.5.3 The Column-Address Decoder 1045 11.6 R e a d - O n l y M e m o r y ( R O M ) 1046

11.6.1 A M O S ROM 1047 11.6.2 Mask-Programmable ROMs 1049 11.6.3 Programmable ROMs (PROMs and EPROMs) 1049

11.7 E m i t t e r - C o u p l e d L o g i c ( E C L ) 1052

11.7.1 The Basic Principle 1052 11.7.2 ECL Families 1053 11.7.3 The Basic Gate Circuit 1053 11.7.4 Voltage Transfer Characteristics 1057 11.7.5 Fan-Out 1061

11.7.6 Speed of Operation and Signal Transmission 1062 11.7.7 Power Dissipation 1063

11.7.8 Thermal Effects 1063 11.7.9 The Wired-OR Capability 1066 11.7.10 Some Final Remarks 1066 11.8 B i C M O S D i g i t a l C i r c u i t s 1067

11.8.1 The BiCMOS Inverter 1067 11.8.2 Dynamic Operation 1069 11.8.3 BiCMOS Logic Gates 1070 11.9 S P I C E S i m u l a t i o n E x a m p l e 1071

S u m m a r y 1076

P r o b l e m s 1077

I n t r o d u c t i o n 1083 12.1 Filter T r a n s m i s s i o n , T y p e s , a n d Specification 1084

12.1.1 Filter Transmission 1084 12.1.2 Filter Types 1085 12.1.3 Filter Specification 1085 12.2 T h e Filter Transfer F u n c t i o n 1088 12.3 B u t t e r w o r t h a n d C h e b y s h e v Filters 1091

12.3.1 The Butterworth Filter 1091 12.3.2 The Chebyshev Filter 1095 12A F i r s t - O r d e r and S e c o n d - O r d e r Filter F u n c t i o n s 1098

12.4.1 First-Order Filters 1098 12.4.2 Second-Order Filter Functions 1101 12.5 T h e S e c o n d - O r d e r L C R R e s o n a t o r 1106 12.5 A The Resonator Natural Modes 1106 12.5.2 Realization of Transmission Zeros 1107 12.5.3 Realization of the Low-Pass Function 1108 12.5.4 Realization of the High-Pass Function 1108 12.5.5 Realization of the Bandpass Function 1108 12.5.6 Realization of the Notch Functions 1110 12.5.7 Realization of the All-Pass Function 1111

12.6 S e c o n d - O r d e r A c t i v e Filters B a s e d o n I n d u c t o r

R e p l a c e m e n t 1112 12.6.1 The Antoniou Inductance-Simulation Circuit 1112 12.6.2 The Op A m p - R C Resonator 1114

12.6.3 Realization of the Various Filter Types 1114 12.6.4 The All-Pass Circuit 1118

12.7 S e c o n d - O r d e r A c t i v e Filters B a s e d o n t h e T w o - I n t e g r a t o r - L o o p

T o p o l o g y 1120 12.7.1 Derivation of the Two-Integrator-Loop Biquad 1120 12.1.2 Circuit Implementation 1122

D E T A I L E D T A B L E O F C O N T E N T S „ j X

12.7.3 An Alternative Two-Integrator-Loop Biquad

Circuit 1123 12.7 A Final Remarks 1125 12.8 S i n g l e - A m p l i f i e r B i q u a d r a t i c A c t i v e Filters 1125

12.8.1 Synthesis of the Feedback Loop 1126 12.8.2 Injecting the Input Signal 1128 12.8.3 Generation of Equivalent Feedback Loops 1130 12.9 Sensitivity 1133

12.10 S w i t c h e d - C a p a c i t o r Filters 1136

12.10.1 The Basic Principle 1136 12.10.2 Practical Circuits 1137 12.10.3 A Final Remark 1141 12.11 T u n e d A m p l i f i e r s 1141

12.11.1 The Basic Principle 1141 12.11.2 Inductor Losses 1143 12.11.3 Use of Transformers 1144 12.11.4 Amplifiers with Multiple Tuned Circuits 1145 12.11.5 The Cascode and the C C - C B Cascade 1146 12.11.6 Synchronous Tuning 1147

12.11.7 Stagger-Timing 1148 12.12 S P I C E S i m u l a t i o n E x a m p l e s 1152

S u m m a r y 1158

P r o b l e m s 1159

I n t r o d u c t i o n 1165 13.1 B a s i c P r i n c i p l e s of S i n u s o i d a l Oscillators 1166

13.1.1 The Oscillator Feedback Loop 1166 13.1.2 The Oscillation Criterion 1167 13.1.3 Nonlinear Amplitude Control 1168 13.1 A A Popular Limiter Circuit for Amplitude Control 1169 13.2 O p A m p - R C O s c i l l a t o r Circuits 1171

13.2.1 The Wien-Bridge Oscillator 1171 13.2.2 The Phase-Shift Oscillator 1174 13.2.3 The Quadrature Oscillator 1176 13.2.4 The Active-Filter-Tuned Oscillator 1177 13.2.5 A Final Remark 1179

13.3 L C a n d C r y s t a l Oscillators 7 7 7 9

13.3.1 LC-Tuned Oscillators 7779

13.3.2 Crystal Oscillators 1182 13.4 B i s t a b l e M u l t i v i b r a t o r s 1185

13.4.1 The Feedback Loop 1185 13.4.2 Transfer Characteristics of the Bistable Circuit 1186 13.4.3 Triggering the Bistable Circuit 1187

13 A A The Bistable Circuit as a Memory Element 1188

13.4.5 A Bistable Circuit with Noninverting Transfer '

X X ! D E T A I L E D T A B L E O F C O N T E N T S

14.6.3 Power Dissipation Versus Temperature 1250 14.6.4 Transistor Case and Heat Sink 1251 14.6.5 The BJT Safe Operating Area 1254 14.6.6 Parameter Values of Power Transistors 1255 14.7 V a r i a t i o n s o n t h e C l a s s A B C o n f i g u r a t i o n 1256 14.7.1 Use of Input Emitter Followers 1256 14.7.2 Use of Compound Devices 1257 14.7.3 Short-Circuit Protection 1259 14.7 A Thermal Shutdown 1260 14.8 I C P o w e r A m p l i f i e r s 1261 14.8.1 A Fixed-Gain IC Power Amplifier 1261 14.8.2 Power Op Amps 1265

14.8.3 The Bridge Amplifier 1265 14.9 M O S P o w e r T r a n s i s t o r s 1266

14.9.1 Structure of the Power MOSFET 1266 14.9.2 Characteristics of Power MOSFETs 1268

14.9.3 Temperature Effects 1269

14.9.4 Comparison with BJTs 1269 14.9.5 A Class AB Output Stage Utilizing MOSFETs 1270 14.10 S P I C E S i m u l a t i o n E x a m p l e 1271

S u m m a r y 1276

P r o b l e m s 1277

A P P E N D I X E S

A VLSI Fabrication Technology A-1

B Two-Port Network Parameters B-1

C S o m e Useful Network Theorems C-1

D Single-Time-Constant Circuits D-1

E s-Domain Analysis: Poles, Zeros, and B o d e Plots E-1

F Bibliography F-1

G Standard Resistance Values and Unit Prefixes G-1

H Answers to Selected Problems H-1

I N D E X IN -1

13.5 G e n e r a t i o n of S q u a r e a n d T r i a n g u l a r W a v e f o r m s U s i n g A s t a b l e

M u l t i v i b r a t o r s 1192 13.5.1 Operation of the Astable Multivibrator 1192 13.5.2 Generation of Triangular Waveforms 1194

13.6 G e n e r a t i o n of a S t a n d a r d i z e d P u l s e — T h e M o n o s t a b l e

M u l t i v i b r a t o r 1196 13.7 I n t e g r a t e d - C i r c u i t T i m e r s 1198 13.7.1 The 555 Circuit 1198 13.7.2 Implementing a Monostable Multivibrator Using the 555 IC 1199 13.7.3 An Astable Multivibrator Using the 555 IC 1201

13.8 N o n l i n e a r W a v e f o r m - S h a p i n g Circuits 1203 13.8.1 The Breakpoint Method 1203

13.8.2 The Nonlinear-Amplification Method 1205 13.9 P r e c i s i o n Rectifier C i r c u i t s 1206

13.9.1 Precision Half-Wave Rectifier-The "Superdiode" 1207 13.9.2 An Alternative Circuit 1208

13.9.3 An Application: Measuring AC Voltages 1209 13.9.4 Precision Full-Wave Rectifier 1210

13.9.5 A Precision Bridge Rectifier for Instrumentation Applications 1212 13.9.6 Precision Peak Rectifiers 1213

13.9.7 A Buffered Precision Peak Detector 1213 13.9.8 A Precision Clamping Circuit 1214 13.10 S P I C E S i m u l a t i o n E x a m p l e s 1214

S u m m a r y 1219

P r o b l e m s 1220

I n t r o d u c t i o n 1229 14.1 Classification of O u t p u t S t a g e s 1230 14.2 C l a s s A O u t p u t S t a g e 1231

14.2.1 Transfer Characteristic 1231 14.2.2 Signal Waveforms 1233 14.2.3 Power Dissipation 1233 14.2.4 Power-Conversion Efficiency 1235 14.3 C l a s s B O u t p u t S t a g e 1235

14.3.1 Circuit Operation 1236 14.3.2 Transfer Characteristic 1236 14.3.3 Power-Conversion Efficiency 1236 14.3.4 Power Dissipation 1238

14.3.5 Reducing Crossover Distortion 1240 14.3.6 Single-Supply Operation 1240 14.4 C l a s s A B O u t p u t S t a g e 1241 14.4.1 Circuit Operation 1242

14.4.2 Output Resistance 1243

14.5 B i a s i n g t h e C l a s s A B C i r c u i t 1244

14.5.1 Biasing Using Diodes 1 2 4 4

14.5.2 Biasing Using the V BE Multiplier 1246 14.6 P o w e r B J T s 1249

14.6.1 Junction Temperature 1249 14.6.2 Thermal Resistance 1249

Microelectronic Circuits, fifth edition, is i n t e n d e d as a text for t h e c o r e c o u r s e s in e l e c t r o n i c

circuits t a u g h t to m a j o r s in electrical a n d c o m p u t e r e n g i n e e r i n g It s h o u l d a l s o p r o v e useful

t o e n g i n e e r s a n d o t h e r p r o f e s s i o n a l s w i s h i n g t o u p d a t e their k n o w l e d g e t h r o u g h self-study

A s w a s t h e c a s e w i t h t h e first four e d i t i o n s , t h e o b j e c t i v e of this b o o k is to d e v e l o p i n t h e

r e a d e r t h e ability t o a n a l y z e and d e s i g n e l e c t r o n i c circuits, b o t h a n a l o g a n d digital, d i s c r e t e

T h e p r e r e q u i s i t e for s t u d y i n g t h e m a t e r i a l in this b o o k is a first c o u r s e i n circuit analysis A s

a review, s o m e linear circuits m a t e r i a l is i n c l u d e d h e r e i n a p p e n d i x e s : specifically, t w o - p o r t

2 E a c h c h a p t e r is o r g a n i z e d so that t h e e s s e n t i a l " m u s t - c o v e r " t o p i c s are p l a c e d first,

a n d t h e m o r e s p e c i a l i z e d m a t e r i a l a p p e a r s last T h i s allows c o n s i d e r a b l e flexibility i n

t e a c h i n g a n d l e a r n i n g f r o m t h e b o o k

3 C h a p t e r 4, M O S F E T s , and C h a p t e r 5, B J T s , h a v e b e e n c o m p l e t e l y rewritten, updated,

and m a d e c o m p l e t e l y i n d e p e n d e n t of e a c h other T h e M O S F E T chapter is placed first t o

reflect t h e fact that it is currently t h e m o s t significant electronics device b y a w i d e m a r ­

gin H o w e v e r , if desired, the B J T can b e c o v e r e d first Also, the identical structure of

the t w o chapters m a k e s teaching a n d learning about t h e s e c o n d d e v i c e easier and faster

x x i i i

x x i v PREFACE

4 T o m a k e t h e first c o u r s e c o m p r e h e n s i v e , b o t h C h a p t e r s 4 a n d 5 i n c l u d e m a t e r i a l on amplifier a n d digital-logic circuits I n a d d i t i o n , t h e f r e q u e n c y r e s p o n s e of t h e b a s i c

c o m m o n - s o u r c e ( c o m m o n - e m i t t e r ) amplifier is i n c l u d e d T h i s is i m p o r t a n t for stu­

d e n t s w h o m i g h t n o t t a k e a s e c o n d c o u r s e in e l e c t r o n i c s

5 A n e w c h a p t e r o n i n t e g r a t e d - c i r c u i t (IC) amplifiers ( C h a p t e r 6) is a d d e d It b e g i n s

w i t h a c o m p r e h e n s i v e c o m p a r i s o n b e t w e e n t h e M O S F E T a n d t h e B J T T y p i c a l

p a r a m e t e r v a l u e s of d e v i c e s p r o d u c e d b y m o d e r n s u b m i c r o n fabrication p r o c e s s e s a r e given a n d utilized in t h e e x a m p l e s , e x e r c i s e s , a n d e n d - o f - c h a p t e r p r o b l e m s T h e study

1 1 T h e S P I C E sections h a v e b e e n r e w r i t t e n a n d t h e S P I C E e x a m p l e s n o w utilize s c h e ­

m a t i c entry T o e n a b l e further e x p e r i m e n t a t i o n , t h e files for all S P I C E e x a m p l e s are

p r o v i d e d o n t h e C D a n d w e b s i t e

THE CD-ROM AND THE WEBSITE

A C D - R O M a c c o m p a n i e s this book It contains m u c h useful s u p p l e m e n t a r y information a n d material intended to enrich the s t u d e n t ' s learning e x p e r i e n c e T h e s e i n c l u d e (1) A S t u d e n t ' s Edition of O r C A D P S p i c e 9.2 (2) T h e input files for all t h e S P I C E e x a m p l e s in this b o o k (3) A link to the b o o k ' s website accessing P o w e r P o i n t slides of e v e r y figure in this b o o k that students c a n print a n d carry to class to facilitate t a k i n g n o t e s (4) B o n u s text material of spe­

cialized topics not c o v e r e d in the current edition of t h e textbook T h e s e include: J F E T s , G a A s devices a n d circuits, a n d T T L c k c u i t s

A w e b s i t e for t h e b o o k h a s b e e n set u p ( w w w s e d r a s m i t h o r g ) Its c o n t e n t will c h a n g e frequently t o reflect n e w d e v e l o p m e n t s in t h e field It features S P I C E m o d e l s a n d files for all P S p i c e e x a m p l e s , l i n k s to industrial a n d a c a d e m i c w e b s i t e s of interest, a n d a m e s s a g e

m o r e design e x a m p l e s , e x e r c i s e p r o b l e m s , a n d e n d - o f - c h a p t e r p r o b l e m s T h o s e exercises and

e n d - o f - c h a p t e r p r o b l e m s that are c o n s i d e r e d " d e s i g n - o r i e n t e d " are i n d i c a t e d with a D A l s o , the m o s t v a l u a b l e design aid, S P I C E , is utilized t h r o u g h o u t the b o o k , as already outlined

EXERCISES, END-OF-CHAPTER PROBLEMS, AND ADDITIONAL SOLVED PROBLEMS

O v e r 4 5 0 e x e r c i s e s a r e i n t e g r a t e d t h r o u g h o u t t h e text T h e a n s w e r t o e a c h e x e r c i s e is g i v e n

b e l o w t h e e x e r c i s e so students c a n c h e c k their u n d e r s t a n d i n g of t h e m a t e r i a l as t h e y r e a d

S o l v i n g t h e s e e x e r c i s e s s h o u l d e n a b l e t h e r e a d e r t o g a u g e h i s or h e r g r a s p of t h e p r e c e d i n g

m a t e r i a l In a d d i t i o n , m o r e t h a n 1 3 7 0 e n d - o f - c h a p t e r p r o b l e m s , a b o u t a third of w h i c h are

n e w t o this edition, a r e p r o v i d e d T h e p r o b l e m s a r e k e y e d t o t h e i n d i v i d u a l s e c t i o n s a n d their

d e g r e e of difficulty is i n d i c a t e d b y a rating s y s t e m : difficult p r o b l e m s a r e m a r k e d w i t h as asterisk (*); m o r e difficult p r o b l e m s w i t h t w o a s t e r i s k s (**); a n d v e r y difficult ( a n d / o r t i m e

c o n s u m i n g ) p r o b l e m s w i t h t h r e e asterisks (***) W e m u s t a d m i t , h o w e v e r , that this classifi­

c a t i o n is b y n o m e a n s exact O u r rating n o d o u b t h a d d e p e n d e d t o s o m e d e g r e e o n o u r t h i n k ­ing ( a n d m o o d ! ) at the t i m e a p a r t i c u l a r p r o b l e m w a s created A n s w e r s t o a b o u t half t h e

p r o b l e m s are g i v e n i n A p p e n d i x H C o m p l e t e s o l u t i o n s for all e x e r c i s e s a n d p r o b l e m s are

i n c l u d e d in t h e Instructor's Manual, w h i c h is a v a i l a b l e f r o m t h e p u b l i s h e r for t h o s e i n s t r u c ­

tors w h o a d o p t t h e b o o k

A s in t h e p r e v i o u s four e d i t i o n s , m a n y e x a m p l e s a r e i n c l u d e d T h e e x a m p l e s , a n d i n d e e d

m o s t of t h e p r o b l e m s a n d e x e r c i s e s , a r e b a s e d on real circuits a n d a n t i c i p a t e t h e a p p l i c a t i o n s

e n c o u n t e r e d i n d e s i g n i n g real-life circuits T h i s e d i t i o n c o n t i n u e s t h e u s e of n u m b e r e d solu­

tion steps in t h e figures for m a n y e x a m p l e s , as an a t t e m p t t o r e c r e a t e t h e d y n a m i c s of t h e

c l a s s r o o m

A r e c u r r i n g r e q u e s t f r o m m a n y of t h e students w h o u s e d earlier e d i t i o n s of t h e b o o k h a s

b e e n for s o l v e d p r o b l e m s T o satisfy this n e e d , a b o o k of a d d i t i o n a l p r o b l e m s w i t h solutions

is a v a i l a b l e w i t h this e d i t i o n (see t h e list of a v a i l a b l e ancillaries later in this p r e f a c e )

AN OUTLINE FOR THE READER

T h e b o o k starts w i t h an i n t r o d u c t i o n to the b a s i c c o n c e p t s of e l e c t r o n i c s in C h a p t e r 1 S i g ­nals, t h e i r f r e q u e n c y spectra, a n d their a n a l o g a n d digital f o r m s a r e p r e s e n t e d A m p l i f i e r s are i n t r o d u c e d as circuit b u i l d i n g b l o c k s a n d their v a r i o u s t y p e s a n d m o d e l s a r e studied T h e basic e l e m e n t of digital electronics, the digital logic inverter, is defined in terms of its voltage-transfer c h a r a c t e r i s t i c , a n d its v a r i o u s i m p l e m e n t a t i o n s u s i n g v o l t a g e a n d c u r r e n t s w i t c h e s are d i s c u s s e d T h i s c h a p t e r a l s o e s t a b l i s h e s s o m e of t h e t e r m i n o l o g y a n d c o n v e n t i o n s u s e d

t h r o u g h o u t t h e text

T h e n e x t four c h a p t e r s a r e d e v o t e d t o t h e study of e l e c t r o n i c d e v i c e s a n d b a s i c circuits

a n d c o n s t i t u t e t h e b u l k of P a r t I of the text C h a p t e r 2 d e a l s w i t h o p e r a t i o n a l amplifiers, their

t e r m i n a l c h a r a c t e r i s t i c s , s i m p l e a p p l i c a t i o n s , a n d l i m i t a t i o n s W e h a v e c h o s e n t o discuss t h e

o p a m p as a circuit b u i l d i n g b l o c k at this early s t a g e s i m p l y b e c a u s e it is e a s y t o d e a l with

a n d b e c a u s e t h e s t u d e n t c a n e x p e r i m e n t w i t h o p - a m p circuits' that p e r f o r m n o n t r i v i a l t a s k s with r e l a t i v e e a s e and w i t h a s e n s e of a c c o m p l i s h m e n t W e h a v e found this a p p r o a c h t o b e

h i g h l y m o t i v a t i n g t o t h e student W e s h o u l d p o i n t out, h o w e v e r , that p a r t or all of this c h a p ­ter c a n b e skipped and studied at a later stage (for instance in conjunction with Chapter 7, Chapter 8, and/or C h a p t e r 9) with n o loss of c o n t i n u i t y

C h a p t e r 3 is d e v o t e d t o t h e study of t h e m o s t f u n d a m e n t a l e l e c t r o n i c d e v i c e , the / ? « j u n c ­tion d i o d e T h e d i o d e t e r m i n a l characteristics and its h i e r a r c h y of m o d e l s and b a s i c circuit

h a v e a n i d e n t i c a l structure and are c o m p l e t e l y i n d e p e n d e n t of e a c h o t h e r a n d t h u s , c a n b e

c o v e r e d in either order E a c h c h a p t e r b e g i n s w i t h a study of t h e d e v i c e structure a n d its

p h y s i c a l o p e r a t i o n , l e a d i n g t o a d e s c r i p t i o n of its t e r m i n a l c h a r a c t e r i s t i c s T h e n , t o e s t a b l i s h

in t h e r e a d e r a h i g h d e g r e e of familiarity w i t h t h e o p e r a t i o n of t h e transistor as a circuit ele­

m e n t , a l a r g e n u m b e r of e x a m p l e s are p r e s e n t e d of d c circuits utilizing t h e d e v i c e T h e

l a r g e - s i g n a l o p e r a t i o n of t h e b a s i c c o m m o n - s o u r c e ( c o m m o n - e m i t t e r ) circuit is t h e n s t u d i e d

a n d u s e d t o d e l i n e a t e t h e r e g i o n o v e r w h i c h t h e d e v i c e c a n b e u s e d as a linear amplifier f r o m

t h o s e r e g i o n s w h e r e it c a n b e u s e d as a s w i t c h T h i s m a k e s clear t h e n e e d for b i a s i n g t h e transistor a n d l e a d s n a t u r a l l y to the study of b i a s i n g m e t h o d s A t this point, t h e b i a s i n g

m e t h o d s u s e d a r e m o s t l y for discrete circuits, l e a v i n g t h e study of I C b i a s i n g t o C h a p t e r 6

N e x t , s m a l l - s i g n a l o p e r a t i o n is s t u d i e d a n d s m a l l - s i g n a l m o d e l s are d e r i v e d T h i s is fol­

l o w e d b y a study of t h e b a s i c c o n f i g u r a t i o n s of discrete-circuit amplifiers T h e i n t e r n a l

c a p a c i t i v e effects that limit the h i g h - f r e q u e n c y o p e r a t i o n of t h e transistor a r e t h e n studied,

a n d t h e h i g h - f r e q u e n c y e q u i v a l e n t - c i r c u i t m o d e l is p r e s e n t e d T h i s m o d e l is t h e n u s e d t o

d e t e r m i n e t h e h i g h - f r e q u e n c y r e s p o n s e of-a c o m m o n - s o u r c e ( c o m m o n - e m i t t e r ) amplifier

A s w e l l , t h e l o w - f r e q u e n c y r e s p o n s e r e s u l t i n g f r o m t h e u s e of c o u p l i n g and b y p a s s c a p a c i ­tors is also p r e s e n t e d T h e b a s i c digital-logic i n v e r t e r circuit is t h e n studied B o t h c h a p t e r s

c o n c l u d e w i t h a study of the transistor m o d e l s u s e d in S P I C E t o g e t h e r with circuit-simulation

e x a m p l e s u s i n g P S p i c e T h i s d e s c r i p t i o n s h o u l d i n d i c a t e that C h a p t e r s 4 a n d 5 c o n t a i n t h e essential m a t e r i a l for a first c o u r s e in e l e c t r o n i c s

P a r t II: A n a l o g a n d D i g i t a l I n t e g r a t e d C i r c u i t s ( C h a p t e r s 6 - 1 0 ) b e g i n s w i t h a c o m p r e ­

h e n s i v e c o m p i l a t i o n a n d c o m p a r i s o n of t h e p r o p e r t i e s of t h e M O S F E T a n d t h e B J T T h e

c o m p a r i s o n is facilitated b y t h e p r o v i s i o n of t y p i c a l p a r a m e t e r v a l u e s of d e v i c e s f a b r i c a t e d

w i t h m o d e r n p r o c e s s t e c h n o l o g i e s F o l l o w i n g a study of b i a s i n g m e t h o d s e m p l o y e d i n I C amplifier d e s i g n ( S e c t i o n 6.3), a n d s o m e b a s i c b a c k g r o u n d m a t e r i a l for t h e a n a l y s i s of h i g h -

f r e q u e n c y amplifier r e s p o n s e ( S e c t i o n 6.4), t h e v a r i o u s c o n f i g u r a t i o n s of s i n g l e - s t a g e I C amplifiers are p r e s e n t e d in a s y s t e m a t i c m a n n e r I n e a c h c a s e , t h e M O S circuit is p r e s e n t e d first S o m e t r a n s i s t o r - p a i r configurations that are u s u a l l y treated as a s i n g l e stage, s u c h as

t h e c a s c o d e a n d t h e D a r l i n g t o n circuits, a r e a l s o studied E a c h section i n c l u d e s a study of t h e

h i g h - f r e q u e n c y r e s p o n s e of t h e particular amplifier c o n f i g u r a t i o n A g a i n , w e b e l i e v e that this " i n - s i t u " study of f r e q u e n c y r e s p o n s e is s u p e r i o r to the traditional a p p r o a c h of p o s t p o n ­ing all c o v e r a g e of f r e q u e n c y r e s p o n s e to a later c h a p t e r A s in o t h e r c h a p t e r s , the m o r e s p e ­cialized m a t e r i a l , i n c l u d i n g a d v a n c e d c u r r e n t - m i r r o r a n d c u r r e n t - s o u r c e c o n c e p t s , is p l a c e d

in t h e s e c o n d half of t h e chapter, a l l o w i n g t h e r e a d e r t o s k i p s o m e of this m a t e r i a l in a first

r e a d i n g T h i s c h a p t e r s h o u l d p r o v i d e an excellent p r e p a r a t i o n for an in-depth study of a n a l o g

n e g a t i v e f e e d b a c k are p r e s e n t e d W e also d i s c u s s t h e stability p r o b l e m in f e e d b a c k amplifi­

ers and treat f r e q u e n c y c o m p e n s a t i o n in s o m e detail

V L S I circuits

T h e n e x t t w o c h a p t e r s of Part III, C h a p t e r s 12 a n d 13, are a p p l i c a t i o n or s y s t e m oriented

C h a p t e r 12 is d e v o t e d to the study of analog-filter design and tuned amplifiers Chapter 13 p r e ­sents a study of sinusoidal' oscillators, w a v e f o r m generators, and other nonlinear signal-pro­

The First Course

T h e m o s t o b v i o u s p a c k a g e for t h e first c o u r s e consists of C h a p t e r s 1 t h r o u g h 5 H o w e v e r , if

t i m e is l i m i t e d , s o m e or all of t h e f o l l o w i n g s e c t i o n s can b e p o s t p o n e d to t h e s e c o n d c o u r s e : 1.6, 1.7, 2.6, 2 7 , 2 8 , 3.6, 3 8 , 4 8 , 4 9 , 4 1 0 , 4 1 1 , 5.8, 5.9, and 5.10 It is also q u i t e p o s s i b l e

t o o m i t C h a p t e r 2 a l t o g e t h e r from this c o u r s e A l s o , it is p o s s i b l e t o c o n c e n t r a t e on t h e

M O S F E T ( C h a p t e r 4) a n d c o v e r t h e B J T ( C h a p t e r 5) only partially a n d / o r m o r e q u i c k l y

C o v e r i n g C h a p t e r 5 t h o r o u g h l y a n d C h a p t e r 4 o n l y partially a n d / o r m o r e q u i c k l y is also

p o s s i b l e — b u t n o t r e c o m m e n d e d ! A n entirely a n a l o g first c o u r s e is also p o s s i b l e b y o m i t t i n g

S e c t i o n s 1.7, 4 1 0 , a n d 5.10 A digitally o r i e n t e d first c o u r s e is also p o s s i b l e It w o u l d c o n ­sist of t h e f o l l o w i n g s e c t i o n s ; 1.1, 1.2, 1.3, 1.4, 1.7, 1.8, 3 1 , 3.2, 3 3 , 3.4, 3.7, 4 1 , 4 2 , 4 3 ,

REFACE

Chapters 6 t h r o u g h 10 (assuming, of course, that t h e first course c o v e r e d Chapters 1 t h r o u g h 5)

If t i m e is short, either C h a p t e r 10 c a n p o s t p o n e d to a s u b s e q u e n t c o u r s e o n digital circuits

A c o m p l e t e set of ancillary m a t e r i a l s is a v a i l a b l e w i t h this text to s u p p o r t y o u r c o u r s e

For the Instructor

T h e Instructor's Manual with Transparency Masters p r o v i d e s c o m p l e t e w o r k e d solutions t o

all t h e e x e r c i s e s in e a c h c h a p t e r a n d all t h e e n d - o f - c h a p t e r p r o b l e m s in t h e text It also

c o n t a i n s 2 0 0 t r a n s p a r e n c y m a s t e r s that d u p l i c a t e t h e figures in t h e text m o s t often u s e d

in c l a s s

1A set of Transparency Acetates of t h e 2 0 0 m o s t i m p o r t a n t figures in t h e b o o k

A PowerPoint CD w i t h slides of every figure i n t h e b o o k a n d e a c h c o r r e s p o n d i n g c a p t i o n

For the Student and the Instructor

T h e CD-ROM i n c l u d e d w i t h every n e w c o p y of t h e t e x t b o o k c o n t a i n s S P I C E i n p u t files, a

M a n y of t h e c h a n g e s in this fifth edition w e r e m a d e in r e s p o n s e t o f e e d b a c k r e c e i v e d f r o m

s o m e of t h e instructors w h o a d o p t e d t h e fourth edition W e are grateful to all t h o s e w h o t o o k

t h e t i m e to w r i t e t o u s In addition, t h e following r e v i e w e r s p r o v i d e d detailed c o m m e n t a r y on

t h e fourth edition a n d s u g g e s t e d m a n y of t h e c h a n g e s that w e h a v e i n c o r p o r a t e d in this r e v i ­

sion T o all of t h e m , w e e x t e n d o u r sincere t h a n k s : M a u r i c e A b u r d e n e , B u c k n e l l U n i v e r s i t y ;

F r i e d m a n , U n i v e r s i t y of R o c h e s t e r ; R h e t t T G e o r g e , Jr., D u k e U n i v e r s i t y ; R i c h a r d H o r n sey, Y o r k U n i v e r s i t y ; R o b e r t Irvine, California State U n i v e r s i t y , P a m o n a ; J o h n K h o u r y ,

U n i v e r s i t y P r e s s t o distribute O r C a d F a m i l y R e l e a s e 9.2 L i t e E d i t i o n software w i t h this

b o o k W e are grateful t o J o h n G e e n from A n a l o g D e v i c e s for p r o v i d i n g t h e c o v e r p h o t o a n d

t o T o m M c E l w e e (from T W M Research)

A l a r g e n u m b e r of p e o p l e at O x f o r d U n i v e r s i t y P r e s s c o n t r i b u t e d to t h e d e v e l o p m e n t of this e d i t i o n a n d its v a r i o u s ancillaries W e w o u l d like t o specifically m e n t i o n B a r b a r a

W a s s e r m a n , L i z a M u r p h y , M a r y B e t h Jarrad, M a c H a w k i n s , B a r b a r a B r o w n , C a t h l e e n

B e n n e t t , C e l e s t e A l e x a n d e r , C h r i s Critelli, E v e Siegel, M a r y H o p k i n s , J e a n n e A m b r o s i o , Trent H a y w o o d , Jennifer Slomack, N e d Escobar, J i m B r o o k s , D e b b i e A g e e , S y l v i a Parrish,

L e e R o z a k i s , K a t h l e e n K e l l y , S h e r i d a n Orr, a n d K e r r y C a h i l l

W e w i s h t o e x t e n d special t h a n k s t o o u r P u b l i s h e r at O x f o r d U n i v e r s i t y P r e s s , C h r i s

R o g e r s W e are also grateful t o S c o t t B u r n s , M a r k e t i n g a n d Sales D i r e c t o r , for h i s m a n y

e x c e l l e n t and c r e a t i v e i d e a s a n d for h i s friendship W e r e c e i v e d a g r e a t d e a l of s u p p o r t and

a d v i c e f r o m o u r p r e v i o u s editor a n d friend, P e t e r G o r d o n After P e t e r ' s d e p a r t u r e , t h e l e a d ­

P a r t I, Devices and Basic Circuits, i n c l u d e s t h e m o s t f u n d a m e n t a l a n d e s s e n t i a l t o p i c s

for t h e study of e l e c t r o n i c circuits A t t h e s a m e t i m e , it c o n s t i t u t e s a c o m p l e t e p a c k

-a g e for -a first c o u r s e o n t h e subject

B e s i d e s silicon d i o d e s a n d transistors, t h e b a s i c e l e c t r o n i c d e v i c e s , t h e o p a m p is

s t u d i e d i n P a r t I A l t h o u g h n o t an e l e c t r o n i c d e v i c e i n t h e m o s t f u n d a m e n t a l s e n s e ,

t h e o p a m p is c o m m e r c i a l l y available as a n i n t e g r a t e d circuit ( I C ) p a c k a g e a n d h a s well-defined t e r m i n a l c h a r a c t e r i s t i c s T h u s , d e s p i t e t h e fact that t h e o p a m p ' s internal circuit is c o m p l e x , t y p i c a l l y i n c o r p o r a t i n g 2 0 or m o r e t r a n s i s t o r s , its a l m o s t - i d e a l ter-

m i n a l b e h a v i o r m a k e s it p o s s i b l e to treat the o p a m p as a circuit e l e m e n t a n d to u s e it

in t h e d e s i g n of p o w e r f u l circuits, as w e d o in C h a p t e r 2 , w i t h o u t a n y k n o w l e d g e of its i n t e r n a l c o n s t r u c t i o n W e s h o u l d m e n t i o n , h o w e v e r , that t h e study of o p a m p s c a n

T h i s subject is t h e n c o n t i n u e d in Section 4 1 for t h e M O S F E T a n d in S e c t i o n 5.1 for

t h e B JT T a k e n together, t h e s e t h r e e sections p r o v i d e a p h y s i c a l b a c k g r o u n d sufficient for t h e study of e l e c t r o n i c circuits at t h e level p r e s e n t e d in this b o o k

T h e heart of this book, and of any electronics course, is the study of the t w o tor types in u s e today: the M O S field-effect transistor ( M O S F E T ) in Chapter 4 a n d the bipolar junction transistor (BJT) in Chapter 5 T h e s e t w o chapters have b e e n written to b e completely independent of o n e another a n d thus can b e studied in either desired order

transis-Furthermore, the t w o chapters have the s a m e structure, m a k i n g it easier a n d faster to study the second device, as well as to draw comparisons b e t w e e n the t w o device types

C h a p t e r 1 p r o v i d e s b o t h a n i n t r o d u c t i o n t o t h e study of e l e c t r o n i c s a n d a n u m b e r

of i m p o r t a n t c o n c e p t s for t h e study of amplifiers ( S e c t i o n s 1.4-1.6) a n d of digital cuits ( S e c t i o n 1.7)

cirE a c h of t h e five c h a p t e r s c o n c l u d e s w i t h a section o n t h e u s e of S P I C cirE s i m u l a tion i n circuit a n a l y s i s a n d d e s i g n Of p a r t i c u l a r i m p o r t a n c e h e r e a r e t h e d e v i c e m o d -els e m p l o y e d b y S P I C E Finally, n o t e that as i n m o s t of t h e c h a p t e r s of this b o o k , t h e

T h e subject of this b o o k is m o d e r n e l e c t r o n i c s , a field that h a s c o m e t o b e k n o w n as m i c r o ­

e l e c t r o n i c s M i c r o e l e c t r o n i c s refers t o t h e i n t e g r a t e d - c i r c u i t (IC) t e c h n o l o g y that at t h e

t i m e of this w r i t i n g is c a p a b l e of p r o d u c i n g circuits that c o n t a i n m i l l i o n s of c o m p o n e n t s in a

s m a l l p i e c e of silicon ( k n o w n as a silicon c h i p ) w h o s e a r e a is o n t h e o r d e r of 100 m m2 O n e such m i c r o e l e c t r o n i c circuit, for e x a m p l e , is a c o m p l e t e digital c o m p u t e r , w h i c h a c c o r d i n g l y

is k n o w n as a m i c r o c o m p u t e r or, m o r e g e n e r a l l y , a m i c r o p r o c e s s o r

I n this b o o k w e shall study e l e c t r o n i c d e v i c e s that c a n b e u s e d singly (in t h e d e s i g n of

d i s c r e t e c i r c u i t s ) or as c o m p o n e n t s of an i n t e g r a t e d - c i r c u i t (IC) c h i p W e shall study t h e

d e s i g n a n d a n a l y s i s of i n t e r c o n n e c t i o n s of t h e s e d e v i c e s , w h i c h f o r m d i s c r e t e a n d i n t e g r a t e d circuits of v a r y i n g c o m p l e x i t y a n d p e r f o r m a w i d e v a r i e t y of functions W e shall also l e a r n

a b o u t a v a i l a b l e I C c h i p s a n d their application in t h e d e s i g n of e l e c t r o n i c s y s t e m s

T h e p u r p o s e of this first c h a p t e r is to i n t r o d u c e s o m e b a s i c c o n c e p t s a n d t e r m i n o l o g y In particular, w e shall learn a b o u t signals a n d a b o u t o n e of t h e m o s t i m p o r t a n t signal-processing functions e l e c t r o n i c circuits a r e d e s i g n e d t o p e r f o r m , n a m e l y , signal amplification W e shall

t h e n l o o k at m o d e l s for linear amplifiers T h e s e m o d e l s will b e e m p l o y e d i n s u b s e q u e n t

c h a p t e r s in t h e d e s i g n a n d a n a l y s i s of actual amplifier circuits

W h e r e a s t h e amplifier is t h e b a s i c e l e m e n t of a n a l o g circuits, t h e l o g i c inverter p l a y s this

r o l e in digital c i r c u i t s W e shall t h e r e f o r e t a k e a p r e l i m i n a r y l o o k at t h e digital inverter, its circuit function, a n d i m p o r t a n t characteristics

e r s ; rather, w e shall a s s u m e that t h e signals of interest a l r e a d y exist in t h e electrical d o m a i n

a n d represent t h e m b y o n e of the t w o equivalent f o r m s s h o w n in F i g 1.1 I n F i g 1.1(a) t h e sig­

n a l is r e p r e s e n t e d b y a v o l t a g e s o u r c e v s (t) h a v i n g a s o u r c e r e s i s t a n c e R s I n t h e alternate

representation of F i g 1.1(b) t h e signal is represented b y a current source i s (t) h a v i n g a s o u r c e

r e s i s t a n c e R s A l t h o u g h t h e t w o r e p r e s e n t a t i o n s a r e e q u i v a l e n t , that in F i g 1.1(a) ( k n o w n a s

t h e T h e v e n i n f o r m ) is preferred w h e n R s is l o w T h e r e p r e s e n t a t i o n of F i g 1.1(b) ( k n o w n as

t h e N o r t o n form) is preferred w h e n R s is h i g h T h e r e a d e r will c o m e t o a p p r e c i a t e this p o i n t

later i n this c h a p t e r w h e n w e study t h e different t y p e s o f amplifiers F o r t h e t i m e b e i n g , it is

i m p o r t a n t t o b e familiar w i t h T h e v e n i n ' s a n d N o r t o n ' s t h e o r e m s (for a brief r e v i e w , s e e

A p p e n d i x D ) a n d t o n o t e t h a t for t h e t w o r e p r e s e n t a t i o n s in F i g 1.1 t o b e e q u i v a l e n t , their

p a r a m e t e r s a r e r e l a t e d b y

»,(/) = R,i,(t)

F r o m t h e d i s c u s s i o n a b o v e , it s h o u l d b e a p p a r e n t that a signal is a t i m e - v a r y i n g q u a n t i t y that c a n b e r e p r e s e n t e d b y a g r a p h such a s that s h o w n in F i g 1.2 I n fact, t h e i n f o r m a t i o n

c o n t e n t of t h e signal is r e p r e s e n t e d b y t h e c h a n g e s i n its m a g n i t u d e as t i m e p r o g r e s s e s ; that

is, t h e i n f o r m a t i o n is c o n t a i n e d i n t h e " w i g g l e s " in t h e signal w a v e f o r m I n g e n e r a l , s u c h

w a v e f o r m s a r e difficult to c h a r a c t e r i z e m a t h e m a t i c a l l y I n o t h e r w o r d s , it is n o t e a s y to

d e s c r i b e succinctly an a r b i t r a r y - l o o k i n g w a v e f o r m such as that of F i g 1.2 O f c o u r s e , s u c h a

-° F I G U R E 1.1 Two alternative representa­

tions of a signal source: (a) the Thevenin

EXERCISES

s M M I o P i t h e signal-source representations shown i n Figs 1.1(a) and 1.1(b) what arc the open-circuit out­

put voltages that would be observed? If, for each, the output terminals are short-circuited (i.e wired

t o g e t h e r ) , w h a t current would flow? For the representations to b e equivalent, what must the relationship

1.2 FREQUENCY SPECTRUM OF SIGNALS

A n e x t r e m e l y useful c h a r a c t e r i z a t i o n of a signal, a n d for that m a t t e r of a n y arbitrary func­

t i o n of t i m e , is in t e r m s of its f r e q u e n c y s p e c t r u m S u c h a d e s c r i p t i o n of signals is o b t a i n e d

t h r o u g h t h e m a t h e m a t i c a l t o o l s of F o u r i e r s e r i e s a n d F o u r i e r t r a n s f o r m 1 W e a r e n o t interested at this p o i n t in t h e details of t h e s e t r a n s f o r m a t i o n s ; suffice it t o s a y that t h e y p r o ­

v i d e t h e m e a n s for r e p r e s e n t i n g a v o l t a g e signal v s (t) or a c u r r e n t signal i s (t) as t h e s u m of

s i n e - w a v e signals of different frequencies a n d a m p l i t u d e s T h i s m a k e s t h e s i n e w a v e a v e r y

i m p o r t a n t signal in t h e a n a l y s i s , design, a n d t e s t i n g o f e l e c t r o n i c circuits T h e r e f o r e , w e shall briefly r e v i e w t h e p r o p e r t i e s of t h e sinusoid

1 The reader who has not yet studied these topics should not be alarmed No detailed application of this material will be made until Chapter 6 Nevertheless, a general understanding of Section 1.2 should be very helpful when studying early parts of this book

8

F I G U R E 1.3 Sine-wave voltage signal of

amplitude V a and frequency / = 1/7* Hz

The angular frequency CO = 2^frad/s

F I G U R E 1 5 The frequency spectrum (also known as the line spectrum) of the periodic square wave

of Fig 1.4

T h e s i n u s o i d a l c o m p o n e n t s in t h e series of E q (1.2) c o n s t i t u t e t h e f r e q u e n c y s p e c t r u m

of t h e s q u a r e - w a v e signal S u c h a s p e c t r u m c a n b e g r a p h i c a l l y r e p r e s e n t e d as in F i g 1.5,

w h e r e t h e h o r i z o n t a l axis r e p r e s e n t s t h e a n g u l a r f r e q u e n c y co in r a d i a n s p e r s e c o n d

T h e F o u r i e r t r a n s f o r m c a n b e a p p l i e d to a n o n p e r i o d i c function of t i m e , such as that

d e p i c t e d i n F i g 1.2, a n d p r o v i d e s its f r e q u e n c y s p e c t r u m as a c o n t i n u o u s function of fre­

q u e n c y , as i n d i c a t e d i n F i g 1.6 U n l i k e t h e c a s e of p e r i o d i c s i g n a l s , w h e r e t h e s p e c t r u m c o n ­

sists of d i s c r e t e f r e q u e n c i e s (at co 0 a n d its h a r m o n i c s ) , t h e s p e c t r u m of a n o n p e r i o d i c signal

c o n t a i n s in g e n e r a l all p o s s i b l e f r e q u e n c i e s N e v e r t h e l e s s , t h e essential p a r t s of t h e s p e c t r a

of p r a c t i c a l signals a r e u s u a l l y c o n f i n e d to relatively short s e g m e n t s of t h e f r e q u e n c y (co)

a x i s — a n o b s e r v a t i o n that is v e r y useful in t h e p r o c e s s i n g of s u c h signals F o r i n s t a n c e , t h e

W e c o n c l u d e this s e c t i o n b y n o t i n g that a signal c a n b e r e p r e s e n t e d either b y t h e m a n n e r

in w h i c h its w a v e f o r m v a r i e s w i t h t i m e , as for t h e v o l t a g e signal v a (t) s h o w n in F i g 1.2, or

i n t e r m s of its f r e q u e n c y s p e c t r u m , as i n F i g 1.6 T h e t w o alternative r e p r e s e n t a t i o n s a r e

k n o w n as t h e t i m e - d o m a i n r e p r e s e n t a t i o n a n d t h e f r e q u e n c y - d o m a i n r e p r e s e n t a t i o n , r e s p e c ­

tively T h e f r e q u e n c y - d o m a i n r e p r e s e n t a t i o n of v a (t) will b e d e n o t e d b y t h e s y m b o l V a ( co)

co (rad/s)

F I G U R E 1 6 The frequency spectrum

of an arbitrary waveform such as that in Fig 1.2

1 O ylSi CHAPTER 1 I N T R O D U C T I O N T O E L E C T R O N I C S

1.3 Find the f r e q u e n c i e s / a n d to of a sine-wave signal with a period of 1 m s

Ans. / ^ 1000 H / : <o - In x 1 03 rad/s

1.4 W h a t is the period T of sine waveforms characterized by frequencies of (a):f = 6 0 H z ? ( b ) / = IQ~' } H z ?

( c ) / = 1 M H z ? \}-]

Ans. 16.7 ms; 1000 s; 1 £is

TiS ; T h e U H F (Ultra High Frequency) television broadcast band begins with channel 14 and extends from

•^.mWJO M H z lo 806 M H z If 6 M H z is allocated for each channel, how manytchannels can this band

a c c o m m o d a t e ?

ssAns 56; channels 14 to 69

1.6 W h e n the square-wave signal of Fig 1.4, whose Fourier series is given in Eq (1.2), is applied to a resistor,

the total p o w e r dissipated m a y be calculated directly using the r e l a t i o n s h i p JP] = 1/T \l{v 1 /R)dl

or indirectly by summing the contribution of each of the harmonic components, that is, P = P , +

P 3 + P5 + • • •, which may be found directly from r m s values Verify that the two approaches are equiv­

alent. What iVacumi o f (he energy of a square wave is in its fundamental? I n its first five harmonics'.' In

its first seven? First nine? In what n u m b e r of harmonics is 9 0 % of the energy? (Note that in counting

harmonies, the fundamental at co 0 is the first, the one at 2ft>„ is the second, etc.)

of t h e s i g n a l of F i g 1.7(a) in t e r m s of its s a m p l e s T h e s i g n a l of F i g 1.7(b) is defined o n l y at

t h e s a m p l i n g i n s t a n t s ; it n o longer is a c o n t i n u o u s function of t i m e , b u t rather, it is a d i s c r e t e

-t i m e signal H o w e v e r , since -the m a g n i -t u d e of e a c h s a m p l e c a n -take a n y v a l u e in a c o n -t i n u o u s

r a n g e , t h e s i g n a l in F i g 1.7(b) is still an a n a l o g signal

N o w if w e r e p r e s e n t the m a g n i t u d e of e a c h of t h e signal s a m p l e s in Fig 1.7(b) b y a n u m ­

b e r h a v i n g a finite n u m b e r of digits, t h e n t h e signal a m p l i t u d e will n o l o n g e r b e c o n t i n u o u s ;

rather, it is said t o b e q u a n t i z e d , d i s c r e t i z e d , or d i g i t i z e d T h e resulting digital signal t h e n is

s i m p l y a s e q u e n c e of n u m b e r s that r e p r e s e n t t h e m a g n i t u d e s of t h e s u c c e s s i v e signal s a m p l e s

T h e c h o i c e of n u m b e r s y s t e m t o r e p r e s e n t t h e s i g n a l s a m p l e s affects t h e t y p e of digital signal p r o d u c e d a n d h a s a p r o f o u n d effect o n t h e c o m p l e x i t y of t h e digital circuits r e q u i r e d

FIGURE 1.7 Sampling the continuous-time analog signal in (a) results in the discrete-time signal in (b)

to p r o c e s s t h e s i g n a l s It turns o u t t h a t t h e b i n a r y n u m b e r s y s t e m results in the s i m p l e s t p o s ­

sible digital signals a n d circuits In a b i n a r y s y s t e m , e a c h digit in t h e n u m b e r takes on o n e of

o n l y t w o p o s s i b l e v a l u e s , d e n o t e d 0 a n d 1 C o r r e s p o n d i n g l y , the digital signals in b i n a r y

s y s t e m s n e e d h a v e o n l y t w o v o l t a g e levels, w h i c h c a n b e labeled l o w and h i g h A s an e x a m p l e ,

i n s o m e of t h e digital circuits studied in this b o o k , t h e levels are 0 V a n d + 5 V F i g u r e 1.8

s h o w s t h e t i m e v a r i a t i o n of such a digital signal O b s e r v e t h a t t h e w a v e f o r m is a p u l s e train

w i t h 0 V r e p r e s e n t i n g a 0 signal, or l o g i c 0, a n d + 5 V r e p r e s e n t i n g l o g i c 1

v (t) A

+ 5

F I G U R E 1 8 Variation of a particular binary digital signal with time

If w e u s e TV b i n a r y digits (bits) to r e p r e s e n t e a c h s a m p l e of the a n a l o g signal, t h e n the

digitized s a m p l e v a l u e c a n b e e x p r e s s e d as

w h e r e b 0 ,b u , b N_i, d e n o t e t h e TV bits a n d h a v e v a l u e s of 0 or 1 H e r e bit b 0 is the l e a s t

s i g n i f i c a n t bit ( L S B ) , a n d bit b N _ l is the m o s t s i g n i f i c a n t b i t ( M S B ) C o n v e n t i o n a l l y , this

b i n a r y n u m b e r is w r i t t e n as b N _ l b N _ 2 b 0 W e o b s e r v e that such a r e p r e s e n t a t i o n q u a n t i z e s

the a n a l o g s a m p l e into o n e of 2 N levels O b v i o u s l y t h e greater the n u m b e r of bits (i.e., t h e

l a r g e r t h e AO, t h e c l o s e r t h e digital w o r d D a p p r o x i m a t e s t h e m a g n i t u d e of t h e a n a l o g

s a m p l e T h a t is, i n c r e a s i n g the n u m b e r of bits r e d u c e s t h e quantization error a n d i n c r e a s e s

the r e s o l u t i o n of t h e analog-to-digital c o n v e r s i o n T h i s i m p r o v e m e n t is, h o w e v e r , u s u a l l y

its i n p u t t h e s a m p l e s of an a n a l o g signal and p r o v i d e s for e a c h input s a m p l e the c o r r e s p o n d ­

ing TV-bit digital r e p r e s e n t a t i o n ( a c c o r d i n g to E q 1.3) at its N o u t p u t t e r m i n a l s T h u s

a l t h o u g h the v o l t a g e at the i n p u t m i g h t b e , say, 6.51 V, at e a c h of t h e output t e r m i n a l s (say,

at t h e ith t e r m i n a l ) , t h e v o l t a g e w i l l b e e i t h e r l o w (0 V) or h i g h (5 V) if b t is s u p p o s e d to b e

0 or 1, r e s p e c t i v e l y W e shall s t u d y t h e A D C a n d its d u a l c i r c u i t t h e d i g i t a l - t o - a n a l o g

c o n v e r t e r ( D / A or D A C ) in C h a p t e r 9

O n c e the signal is in digital form, it c a n b e p r o c e s s e d u s i n g digital c i r c u i t s O f c o u r s e

digital circuits c a n d e a l also w i t h signals that d o n o t h a v e an a n a l o g origin, such as the sig­

nals that r e p r e s e n t t h e v a r i o u s i n s t r u c t i o n s of a digital c o m p u t e r

S i n c e digital circuits deal e x c l u s i v e l y w i t h b i n a r y signals, their d e s i g n is s i m p l e r t h a n

that of a n a l o g circuits F u r t h e r m o r e , digital s y s t e m s c a n b e d e s i g n e d u s i n g a r e l a t i v e l y few

different k i n d s of digital circuit b l o c k s H o w e v e r , a l a r g e n u m b e r (e.g., h u n d r e d s of t h o u ­

s a n d s or e v e n m i l l i o n s ) of e a c h of t h e s e b l o c k s are u s u a l l y n e e d e d T h u s the d e s i g n of digital

circuits p o s e s its o w n set of c h a l l e n g e s to t h e d e s i g n e r b u t p r o v i d e s reliable a n d e c o n o m i c

i m p l e m e n t a t i o n s of a g r e a t variety of signal p r o c e s s i n g functions, s o m e of w h i c h are n o t

p o s s i b l e w i t h a n a l o g circuits A t the p r e s e n t t i m e , m o r e a n d m o r e of t h e signal p r o c e s s i n g

functions are b e i n g p e r f o r m e d digitally E x a m p l e s a r o u n d u s a b o u n d : from the digital w a t c h

a n d t h e c a l c u l a t o r to digital a u d i o s y s t e m s and, m o r e r e c e n t l y , digital television M o r e o v e r ,

s o m e l o n g s t a n d i n g a n a l o g s y s t e m s such as t h e t e l e p h o n e c o m m u n i c a t i o n s y s t e m are n o w

a l m o s t entirely digital A n d w e s h o u l d n o t forget the m o s t i m p o r t a n t of all digital s y s t e m s ,

the digital c o m p u t e r

T h e b a s i c b u i l d i n g b l o c k s of digital s y s t e m s are logic circuits a n d m e m o r y circuits W e

shall s t u d y b o t h i n this b o o k , b e g i n n i n g in S e c t i o n 1.7 w i t h t h e m o s t f u n d a m e n t a l digital

circuit, t h e digital logic inverter

- o by -ob N _

Digital output

F I G U R E 1 9 Block-diagram representation of the analog-to-digital converter (ADC)

(a) Give D corresponding lo v A = 0 V, 1 V, 2 V, and 15 V

(b) What, change in <>,, causes a change from 0 to I in: (i) b n (ii) b v (iii) b 2 , and (iv) £,?

(c) If v A = 5.2 V, what do you expect D to be? What is the resulting error in representation?

Ans fa.) 0 0 0 0 0 0 0 1 nom. 11 1 1 : fb) +1 V +2V +4V +HV: fc) 0 1 0 1 - 4 %

1.4 AMPLIFIERS

I n this section, w e shall i n t r o d u c e a f u n d a m e n t a l s i g n a l - p r o c e s s i n g function that is e m p l o y e d

i n s o m e f o r m in a l m o s t e v e r y electronic s y s t e m , n a m e l y , signal amplification W e shall

s t u d y the amplifier as a circuit b u i l d i n g b l o c k , that is c o n s i d e r its external characteristics a n d

l e a v e t h e d e s i g n of its i n t e r n a l circuit to later c h a p t e r s

1.4.1 Signal Amplification

F r o m a c o n c e p t u a l p o i n t of v i e w t h e s i m p l e s t s i g n a l - p r o c e s s i n g task is that of s i g n a l a m p l i ­

f i c a t i o n T h e n e e d for amplification arises b e c a u s e t r a n s d u c e r s p r o v i d e signals that are said

to b e " w e a k , " that is, i n t h e m i c r o v o l t (/SV) or m i l l i v o l t ( m V ) r a n g e a n d p o s s e s s i n g little

e n e r g y S u c h signals are t o o small for r e l i a b l e p r o c e s s i n g , a n d p r o c e s s i n g is m u c h easier if the signal m a g n i t u d e is m a d e larger T h e functional b l o c k that a c c o m p l i s h e s this t a s k is t h e

s i g n a l a m p l i f i e r

It is a p p r o p r i a t e at this p o i n t to d i s c u s s the n e e d for l i n e a r i t y in amplifiers W h e n a m p l i ­

fying a signal, c a r e m u s t b e e x e r c i s e d so that t h e i n f o r m a t i o n c o n t a i n e d in the signal is not,

c h a n g e d and n o n e w information is introduced T h u s w h e n feeding the signal s h o w n in Fig 1.2

to a n amplifier, w e w a n t t h e o u t p u t signal of t h e amplifier to b e a n e x a c t r e p l i c a of that at t h e input, e x c e p t of c o u r s e for h a v i n g larger m a g n i t u d e I n other w o r d s , t h e " w i g g l e s " in the

w h e r e v t a n d v 0 are t h e input a n d o u t p u t signals, r e s p e c t i v e l y , a n d A is a c o n s t a n t r e p r e s e n t ­

ing t h e m a g n i t u d e of amplification, k n o w n as a m p l i f i e r g a i n E q u a t i o n (1.4) is a linear rela­

t i o n s h i p ; h e n c e t h e amplifier it d e s c r i b e s is a l i n e a r amplifier It should b e e a s y to see that if

the relationship b e t w e e n v a and v- t contains h i g h e r p o w e r s of v { , then the w a v e f o r m of v 0 will

n o longer b e identical to that of v t T h e amplifier is then said to exhibit n o n l i n e a r distortion

c a n b e a c q u i r e d b y reflecting o n t h e p o w e r amplifier A linear p o w e r amplifier c a u s e s b o t h soft a n d l o u d m u s i c p a s s a g e s to b e r e p r o d u c e d w i t h o u t distortion

1.4.2 Amplifier Circuit Symbo!

T h e signal amplifier is o b v i o u s l y a t w o - p o r t n e t w o r k Its function is c o n v e n i e n t l y r e p r e ­

s e n t e d b y t h e circuit s y m b o l of F i g 1.10(a) T h i s s y m b o l clearly d i s t i n g u i s h e s t h e i n p u t a n d

o u t p u t p o r t s a n d indicates t h e direction of signal flow T h u s , in s u b s e q u e n t d i a g r a m s it w i l l

n o t b e n e c e s s a r y t o label t h e t w o p o r t s " i n p u t " a n d " o u t p u t " F o r g e n e r a l i t y w e h a v e s h o w n

t h e amplifier t o h a v e t w o i n p u t t e r m i n a l s t h a t are distinct f r o m t h e t w o o u t p u t t e r m i n a l s A

m o r e c o m m o n situation is illustrated in F i g 1.10(b), w h e r e a c o m m o n t e r m i n a l exists

b e t w e e n t h e i n p u t a n d o u t p u t p o r t s of t h e amplifier T h i s c o m m o n t e r m i n a l is u s e d as a ref­

e r e n c e p o i n t a n d is c a l l e d t h e c i r c u i t g r o u n d

1.4.3 Voltage Gain

A linear amplifier a c c e p t s an i n p u t signal Vj(t) a n d p r o v i d e s at t h e output, across a l o a d

r e s i s t a n c e R L (see F i g 1.11(a)), an o u t p u t signal v 0 (t) that is a m a g n i f i e d r e p l i c a of v,(t)

T h e v o l t a g e g a i n of t h e amplifier is defined b y

F i g 1.11(b) s h o w s t h e t r a n s f e r c h a r a c t e r i s t i c of a linear amplifier If w e apply t o t h e i n p u t

of this amplifier a s i n u s o i d a l v o l t a g e of a m p l i t u d e V, w e obtain at t h e o u t p u t a s i n u s o i d of

a m p l i t u d e A V V

(a) (b)

FIGURE 1 1 0 (a) Circuit symbol for amplifier, (b) An amplifier with a common terminal (ground) between the input and output ports

FIGURE 1 1 1 (a) A voltage amplifier fed with a signal v;(f) and connected to a load resistance R L

(b) Transfer characteristic of a linear voltage amplifier with voltage gain A v

1.4.4 Power Gain and Current Gain

A n amplifier i n c r e a s e s t h e signal p o w e r , an i m p o r t a n t feature that d i s t i n g u i s h e s an amplifier

f r o m a t r a n s f o r m e r In t h e c a s e of a transformer, a l t h o u g h t h e v o l t a g e d e l i v e r e d t o t h e l o a d

c o u l d b e g r e a t e r t h a n t h e v o l t a g e f e e d i n g t h e i n p u t side (the p r i m a r y ) , t h e p o w e r d e l i v e r e d t o the l o a d (from t h e s e c o n d a r y side of t h e transformer) is less than or at m o s t e q u a l to t h e p o w e r

s u p p l i e d b y t h e signal s o u r c e O n t h e o t h e r h a n d , an amplifier p r o v i d e s t h e l o a d w i t h p o w e r

g r e a t e r t h a n that o b t a i n e d f r o m t h e signal s o u r c e T h a t is, amplifiers h a v e p o w e r gain T h e

p o w e r g a i n of t h e amplifier in F i g 1.11(a) is defined as

w h e r e i 0 is t h e current that t h e amplifier delivers t o t h e l o a d (R L ), i 0 = v 0 IR L , a n d z7 is t h e cur­

rent t h e amplifier d r a w s from t h e signal source T h e c u r r e n t g a i n of t h e amplifier is defined as

C u r r e n t g a i n (A,-) = — (1.8)

h

F r o m E q s (1.5) t o (1.8) w e n o t e that

1.4.5 Expressing Gain in Decibels

T h e amplifier g a i n s defined a b o v e are ratios of similarly d i m e n s i o n e d quantities T h u s t h e y will b e e x p r e s s e d e i t h e r as d i m e n s i o n l e s s n u m b e r s or, for e m p h a s i s , as V / V for t h e v o l t a g e

g a i n A / A for t h e c u r r e n t g a i n , a n d W / W for t h e p o w e r gain Alternatively', for a n u m b e r of

r e a s o n s , s o m e of t h e m historic, electronics e n g i n e e r s express amplifier gain with a logarith­

m i c m e a s u r e Specifically t h e v o l t a g e g a i n A v c a n b e e x p r e s s e d as

V o l t a g e gain in d e c i b e l s = 2 0 log | A J d B

difference b e t w e e n i n p u t a n d o u t p u t s i g n a l s ; it d o e s n o t i m p l y that t h e amplifier is a t t e n u a t

-i n g t h e s-ignal O n the other h a n d , a n ampl-if-ier w h o s e v o l t a g e ga-in -is, say, - 2 0 d B -is -in fact

attenuating t h e i n p u t signal b y a factor of 10 (i.e., A v = 0.1 V / V )

1.4.6 The Amplifier Power Supplies

S i n c e t h e p o w e r d e l i v e r e d to t h e l o a d is g r e a t e r t h a n t h e p o w e r d r a w n f r o m t h e signal s o u r c e ,

t h e q u e s t i o n arises as t o t h e s o u r c e of this a d d i t i o n a l p o w e r T h e a n s w e r is f o u n d b y o b s e r v

-i n g that ampl-if-iers n e e d d c p o w e r suppl-ies for the-ir o p e r a t -i o n T h e s e d c s o u r c e s s u p p l y t h e

e x t r a p o w e r d e l i v e r e d to t h e l o a d as w e l l as any p o w e r that m i g h t b e d i s s i p a t e d in t h e nal circuit of t h e amplifier (such p o w e r is c o n v e r t e d to h e a t ) In F i g 1.11(a) w e h a v e n o t explicitly s h o w n t h e s e dc s o u r c e s

inter-F i g u r e 1.12(a) s h o w s an amplifier that r e q u i r e s t w o d c s o u r c e s : o n e p o s i t i v e of v a l u e V x

from t h e n e g a t i v e s u p p l y is I 2 (see Fig 1.12(a)), then t h e d c p o w e r d e l i v e r e d to t h e amplifier is

Pd c = V , / , + V 2 I 2

If t h e p o w e r d i s s i p a t e d i n t h e amplifier circuit is d e n o t e d Pd i s s i p a t e d, t h e p o w e r b a l a n c e e q u a tion for t h e amplifier c a n b e w r i t t e n as

T h e p o w e r efficiency is an i m p o r t a n t p e r f o r m a n c e p a r a m e t e r for amplifiers that h a n d l e l a r g e

a m o u n t s of p o w e r S u c h amplifiers, c a l l e d p o w e r amplifiers, a r e u s e d , for e x a m p l e , as

out-p u t amout-plifiers of s t e r e o s y s t e m s

In o r d e r t o simplify circuit d i a g r a m s , w e shall a d o p t t h e c o n v e n t i o n illustrated in

F i g 1.12(b) H e r e t h e V + t e r m i n a l is s h o w n c o n n e c t e d t o a n a r r o w h e a d p o i n t i n g u p w a r d a n d

t h e V t e r m i n a l t o an a r r o w h e a d p o i n t i n g d o w n w a r d T h e c o r r e s p o n d i n g v o l t a g e is i n d i

c a t e d n e x t to e a c h a r r o w h e a d N o t e that i n m a n y cases w e will n o t explicitly s h o w t h e c o n

-n e c t i o -n s of t h e amplifier t o t h e dc p o w e r s o u r c e s F i -n a l l y , w e -n o t e that s o m e amplifiers

r e q u i r e only o n e p o w e r s u p p l y

Consider an amplifier operating from ± 1 0 - V p o w e r supplies It is fed with a sinusoidal voltage having 1 V peak and delivers a sinusoidal voltage output of 9 V peak to a 1-kQ load T h e ampli-fier draws a current of 9.5 m A from each of its t w o p o w e r supplies T h e input current of the amplifier is found to be sinusoidal with 0.1 m A peak Find the voltage gain, the current gain, the power gain, the p o w e r drawn from the dc supplies, the p o w e r dissipated in the amplifier, and the amplifier efficiency

o u t p u t v o l t a g e c a n n o t e x c e e d a specified p o s i t i v e limit a n d c a n n o t d e c r e a s e b e l o w a specified

n e g a t i v e limit T h e resulting transfer characteristic is s h o w n in Fig 1.13, with t h e p o s i t i v e a n d

1.4 A M P L I F I E R S

negative saturation levels d e n o t e d L+ and L_, respectively E a c h of the t w o saturation levels

is usually within a volt or so of t h e v o l t a g e of t h e corresponding p o w e r supply

O b v i o u s l y , i n o r d e r to a v o i d distorting t h e o u t p u t signal w a v e f o r m , t h e i n p u t signal

s w i n g m u s t b e k e p t w i t h i n t h e linear r a n g e of o p e r a t i o n ,

< Vj < —

F i g u r e 1.13 s h o w s t w o i n p u t w a v e f o r m s and t h e c o r r e s p o n d i n g o u t p u t w a v e f o r m s W e n o t e that t h e p e a k s of t h e larger w a v e f o r m h a v e b e e n c l i p p e d off b e c a u s e of amplifier saturation

1 4 8 Nonlinear Transfer Characteristics and Biasing

E x c e p t for t h e o u t p u t saturation effect d i s c u s s e d a b o v e , t h e amplifier transfer c h a r a c t e r i s t i c s

h a v e b e e n a s s u m e d t o b e perfectly linear I n p r a c t i c a l amplifiers t h e transfer characteristic

m a y e x h i b i t n o n l i n e a r i t i e s of v a r i o u s m a g n i t u d e s , d e p e n d i n g on h o w e l a b o r a t e t h e amplifier circuit is a n d o n h o w m u c h effort h a s b e e n e x p e n d e d in t h e d e s i g n t o e n s u r e linear o p e r a t i o n

C o n s i d e r as a n e x a m p l e t h e transfer c h a r a c t e r i s t i c d e p i c t e d i n F i g 1.14 S u c h a c h a r a c t e r ­

istic is t y p i c a l of s i m p l e amplifiers that are o p e r a t e d f r o m a single (positive) p o w e r s u p p l y

T h e transfer c h a r a c t e r i s t i c is o b v i o u s l y n o n l i n e a r and, b e c a u s e of t h e s i n g l e - s u p p l y o p e r a ­tion, is n o t c e n t e r e d a r o u n d t h e origin F o r t u n a t e l y , a s i m p l e t e c h n i q u e e x i s t s for obtaining linear amplification from an amplifier with such a nonlinear transfer characteristic

a r o u n d t h e d c o p e r a t i n g p o i n t Q I n this w a y , o n e c a n d e t e r m i n e t h e w a v e f o r m of t h e t o t a l

i n s t a n t a n e o u s o u t p u t v o l t a g e v 0 {t) It c a n b e s e e n t h a t b y k e e p i n g t h e a m p l i t u d e of t/,-(f)

sufficiently s m a l l , t h e i n s t a n t a n e o u s o p e r a t i n g p o i n t c a n b e c o n f i n e d t o an a l m o s t linear seg­

m e n t of t h e transfer c u r v e c e n t e r e d a b o u t Q T h i s i n turn results in t h e t i m e - v a r y i n g p o r t i o n

amplifier is operated from a single power supply, V DD

t h e o p e r a t i o n t o b e n o l o n g e r restricted t o a n a l m o s t linear s e g m e n t of t h e transfer c u r v e

T h i s i n t u r n r e s u l t s in a distorted o u t p u t s i g n a l w a v e f o r m S u c h n o n l i n e a r d i s t o r t i o n is

u n d e s i r a b l e : T h e o u t p u t signal contains additional spurious i n f o r m a t i o n that is n o t part of t h e

input W e shall u s e this b i a s i n g t e c h n i q u e a n d t h e a s s o c i a t e d s m a l l - s i g n a l a p p r o x i m a t i o n

frequently in t h e d e s i g n of transistor amplifiers

1.4 A M P L I F I E R S 2 1

A transistor amplifier has the transfer characteristic

which applies for » , > 0 V and v 0 > 0.3 V Find the limits L_ and L+ and the corresponding values

of v, Also, find the value of the dc bias voltage V, that results in V 0 = 5 V and the voltage gain at the corresponding operating point

Solution

The limit L_ is obviously 0.3 V The corresponding value of w7is obtained by substituting v 0 = 0.3 V

in Eq (1.11); that is,

V l = 0.690 V

T h e limit L + is determined by v, = 0 and is thus given by

L + = 1 0 - l O ^1 - 10 V

T o bias the device so that V 0 = 5 V w e require a dc input V, w h o s e value is obtained by substitut­

ing v 0 = 5 V in Eq (1.11) to find:

0.673 0.690

FIGURE 1 1 5 A sketch of the transfer characteristic of the amplifier of Example 1.2

Note that this amplifier is inverting (i.e., with

V[ (V) a gain that is negative)

2 2 J CHAPTER 1 I N T R O D U C T I O N T O E L E C T R O N I C S

t

F I G U R E 1 1 6 Symbol convention employed throughout the book

1.8 An amplifier has a voltage gain of 100 V/V and a current gain of 1000 A/A Express the voltage and

current gains in decibels and find the power gain

^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^

1.9 A n amplifier operating from a single 15-V supply provides a 12-V peak-to-peak sine-wave signal to a

l-kf2 load and draws negligible input current from the signal source The dc current drawn from the 15-V

supply is 8 m A W h a t is the p o w e r dissipated in the amplifier, and what is the amplifier efficiency?

1.10 T h e objective of this exercise is to investigate the limitation of the small-signal approximation Con­sider the amplifier of Example 1.2 with a positive input signal of 1 mV superimposed on the dc bias voltage V', Find the corresponding signal at the output for two situations: (a) A s s u m e the amplifier is linear around the operating point: that is, use the value of gain evaluated in E x a m p l e 1.2 (b) Use the transfer characteristic of the amplifier Repeat for input signals of 5 m V and 10 m V

A n s - 0 2 V , - 0 2 0 4 V: - I V , - 1 1 0 7 V: - 2 V , - 2 4 5 9 V

•: 5 CIRCUIT MODELS FOR AMPLIFIERS

A g o o d p a r t of this b o o k is c o n c e r n e d w i t h t h e d e s i g n of amplifier circuits u s i n g t r a n s i s t o r s

s y m b o l w i t h an u p p e r c a s e subscript, for e x a m p l e , i A (t), v c (t) D i r e c t - c u r r e n t (dc) q u a n t i t i e s

w i l l b e d e n o t e d b y a n u p p e r c a s e s y m b o l w i t h an u p p e r c a s e subscript, for e x a m p l e , I A , V c

P o w e r - s u p p l y (dc) v o l t a g e s are d e n o t e d b y an u p p e r c a s e V w i t h a d o u b l e - l e t t e r u p p e r c a s e subscript, for e x a m p l e , V DD A similar n o t a t i o n is u s e d for t h e dc current d r a w n f r o m t h e

p o w e r s u p p l y , for e x a m p l e , I DD F i n a l l y , i n c r e m e n t a l s i g n a l q u a n t i t i e s w i l l b e d e n o t e d b y a

l o w e r c a s e s y m b o l w i t h a l o w e r c a s e subscript, for e x a m p l e , i a (t), v c (t) If t h e s i g n a l is a sine

w a v e , t h e n its a m p l i t u d e is d e n o t e d b y an u p p e r c a s e letter w i t h a l o w e r c a s e s u b s c r i p t , for

e x a m p l e , I a , V c T h i s n o t a t i o n is illustrated i n F i g 1.16

[c A

i n d i c a t e s a l s o t h a t for R L = «>, A„ = A vo T h u s A m is t h e v o l t a g e gain of t h e u n l o a d e d a m p l i ­

fier, or t h e o p e n - c i r c u i t v o l t a g e g a i n It s h o u l d a l s o b e clear t h a t i n specifying t h e v o l t a g e

g a i n of an amplifier, o n e m u s t also specify t h e v a l u e of l o a d r e s i s t a n c e at w h i c h this g a i n is

r e s i s t a n c e ( m u c h s m a l l e r t h a n t h e l o a d r e s i s t a n c e ) b u t w i t h a m o d e s t v o l t a g e g a i n (or e v e n

u n i t y g a i n ) S u c h a n amplifier is referred t o as a b u f f e r a m p l i f i e r W e shall e n c o u n t e r buffer

amplifiers often t h r o u g h o u t this b o o k

Ans. 10 juV r m s : 1 0 "1 1 W ; 0.25 V; 6.25 m W : - 1 2 d B ; 44 dB

1.12 T h e output voltage of a voltage amplifier has been found to decrease by 2 0 % when a load resistance of

1 Id2 is connected What is the value of the amplifier output resistance?

1.13 A n amplifier with a voltage gain o f + 4 0 d B , an input resistance of 10 k Q , and an output resistance of

1 k Q is used to drive a 1-kQload W h a t is the value of A „ ? Find the value of power gain in d B

v L /v s , the current gain, and the power gain

I I I I

Source I Stage 1 I Stage 2 I Stage 3 I Load

F I G U R E 1 1 8 Three-stage amplifier for Example 1.3

A v2 = ^ = 1 0 0 — = 90.9 V/V

v n 10 k Q + 1 k Q Finally, the voltage gain of the output stage is as follows:

A v3 = ^ = 1 Ml* = 0.909 V/V 1,3 v i3 1 0 0 Q + 1 0 Q

T h e total gain of the three stages in cascade can b e n o w found from

A few c o m m e n t s o n t h e c a s c a d e amplifier in t h e a b o v e e x a m p l e are in order T o a v o i d

l o s i n g s i g n a l s t r e n g t h at the amplifier i n p u t w h e r e t h e signal is u s u a l l y v e r y s m a l l , t h e first stage is d e s i g n e d t o h a v e a relatively l a r g e i n p u t r e s i s t a n c e (1 M Q ) , w h i c h is m u c h l a r g e r than t h e s o u r c e r e s i s t a n c e T h e trade-off a p p e a r s t o b e a m o d e r a t e v o l t a g e g a i n ( 1 0 V / V )

T h e s e c o n d stage d o e s n o t n e e d to h a v e s u c h a h i g h i n p u t r e s i s t a n c e ; rather, h e r e w e n e e d to

r e a l i z e t h e b u l k of t h e r e q u i r e d v o l t a g e g a i n T h e third a n d final, or output, s t a g e is n o t a s k e d

t o p r o v i d e a n y v o l t a g e gain; rather, it functions as a buffer amplifier, p r o v i d i n g a relatively

large i n p u t r e s i s t a n c e a n d a l o w o u t p u t r e s i s t a n c e , m u c h l o w e r t h a n R L It is this s t a g e t h a t

e n a b l e s c o n n e c t i n g the a m p l i f i e r to the 1 0 - Q load T h e s e p o i n t s c a n b e m a d e m o r e c o n c r e t e

b y s o l v i n g t h e f o l l o w i n g e x e r c i s e s

1.14 What would the overall voltage gain of the cascade amplifier in E x a m p l e 1.3 be without stage j ?

1.15 For the cascade amplifier of Example 1.3, let v s be 1 raV Find v ih v, 2 , v, 3 , and v L

Ans. 0.91 mV: 9 mV; 818 mV; 744 raV

1.16 (a) M o d e l the three-stage amplifier of E x a m p l e 1.3 (without the source and load) using the v

amplifier model What are the values of R-„ A,„ and /?„'?

(b) If R L varies in the range 10 Q to 1000 Q , find the corresponding range of the overall voltage gain

1.5.4 Relationships Between the Four Amplifier Models

A l t h o u g h for a g i v e n amplifier a p a r t i c u l a r o n e of t h e four m o d e l s in T a b l e 1.1 is m o s t pref­

erable, any of the four can be used to model the amplifier In fact, s i m p l e r e l a t i o n s h i p s c a n

2 8 îf ' : CHAPTER 1 I N T R O D U C T I O N T O E L E C T R O N I C S

TABLE 1.1 The Four Amplifier Types

o u t p u t r e s i s t a n c e c a n b e f o u n d b y e l i m i n a t i n g t h e i n p u t signal s o u r c e (then a n d v t will b o t h

b e z e r o ) a n d a p p l y i n g a v o l t a g e signal v x t o t h e o u t p u t of t h e amplifier If w e d e n o t e t h e

cur-rent d r a w n f r o m v x into t h e output t e r m i n a l s as i x ( n o t e that i x is o p p o s i t e in direction to i B ),

t h e n R„ = v x li x A l t h o u g h t h e s e t e c h n i q u e s a r e c o n c e p t u a l l y correct, in actual p r a c t i c e m o r e refined m e t h o d s a r e e m p l o y e d in m e a s u r i n g R i a n d R a

T h e amplifier m o d e l s c o n s i d e r e d a b o v e a r e u n i l a t e r a l ; that is, signal flow is u n i d i r e c

T h e bipolar j u n c t i o n transistor (BJT), which will be studied in Chapter 5, is a three-terminal

device that when dc biased and operated with small signals can be modeled by the linear circuit

shown in Fig 1.19(a) T h e three terminals are the base (B), the emitter ( E ) , and the collector ( C )

T h e heart of the model is a transconductance amplifier represented by an input resistance

between B and E (denoted rj, a short-circuit transconductance g m , and an output resistance r„

(c)

FIGURE 1 1 9 (a) Small-signal circuit model for a bipolar junction transistor (BJT). (b) The BJT connected as an amplifier with the emitter as a common terminal between input and output (called a common-emitter amplifier), (c) An alternative small-signal circuit model for the BJT

(a) W i t h t h e emitter u s e d as a c o m m o n terminal b e t w e e n input and output, Fig 1.19(b) shows

a transistor amplifier k n o w n as a common-emitter or grounded-emitter circuit Derive an

expression for the voltage gain vjv s , and evaluate its m a g n i t u d e for the case R s = 5 k Q , r n = 2.5 k Q , g m = 4 0 m A / V , r 0 = 100 k Q , and R L = 5 k Q W h a t would the gain value b e if the effect

of r„ were neglected?

(b) A n alternative m o d e l for the transistor in which a current amplifier rather than a

transconduc-tance amplifier is utilized is shown in Fig 1.19(c) W h a t must the short-circuit current-gain ¡5 be?

Give both an expression and a value

Solution

(a) Using the voltage-divider rule, w e determine the fraction of input signal that appears at the amplifier input as

M N e x t w e d e t e r m i n e the output v o l t a g e v a by multiplying the current (g m v be ) by the resistance

1.17|Consider a current amplifier having the model shown in Ihe second row of Table 1.1 Let the amplifier

,'-fee fed with a signal current-source i s having a resistance R t , and let the output be connected to a load

ie^csistance R,. Show that the overall current gain is given by

1,18 Consider the transconductance amplifier whose model is shown in the third row of Table 1.1 Let a

volt-age signal-source t\ w i t h a source resistance R S b e connected to the input and a load'resistance R L be

-connected to flic output Show thai the overall voltage-gain is given by '

1.6 F R E Q U E N C Y R E S P O N S E O F A M P L I F I E R S ¡ ' 1

1.19 Consider a transresistance amplifier having the m o d e l shown in the third row of Table 1.1 Let the

amplifier b e fed with a signal current-source i s having a resistance R S and let the output b e connected to

a load resistance R L Show that the overall gain is given by

/ R,. - R R • R

; 1i20»Find the input resistance between terminals B and G in the circuit shown in Fig E l 20 T h e voltage v r is

»/ attest voltage with the input resistance R M defined as R IN = v,/i r

Ans.K = , R ^ I/ ? - l K

F I G U R E E l 2 0

1.6 FREQUENCY R E S P O N S E OF AMPLIFIERS

F r o m S e c t i o n 1.2 w e k n o w that t h e i n p u t s i g n a l t o an amplifier c a n a l w a y s b e e x p r e s s e d as the s u m of s i n u s o i d a l s i g n a l s It f o l l o w s t h a t a n i m p o r t a n t c h a r a c t e r i z a t i o n of an amplifier is

in t e r m s of its r e s p o n s e t o i n p u t s i n u s o i d s of different f r e q u e n c i e s S u c h a c h a r a c t e r i z a t i o n of amplifier p e r f o r m a n c e is k n o w n as t h e amplifier f r e q u e n c y r e s p o n s e

1.6.1 Measuring the Amplifier Frequency Response

W e shall i n t r o d u c e t h e subject of amplifier f r e q u e n c y r e s p o n s e b y s h o w i n g h o w it c a n b e

FIGURE 1 2 0 Measuring the frequency response of a linear amplifier At the test frequency co, the amplifier

gain is characterized by its magnitude (V 0 /V^ and phase <p

amplifier o u t p u t a l s o is s i n u s o i d a l w i t h e x a c t l y t h e s a m e f r e q u e n c y co T h i s is an i m p o r t a n t

p o i n t to n o t e : Whenever a sine-wave signal is applied to a linear circuit, the resulting output

is sinusoidal with the same frequency as the input I n fact, t h e s i n e w a v e is t h e o n l y signal

that d o e s n o t c h a n g e s h a p e as it p a s s e s t h r o u g h a l i n e a r circuit O b s e r v e , h o w e v e r , t h a t t h e

o u t p u t sinusoid will i n general h a v e a different a m p l i t u d e a n d will b e shifted i n p h a s e relative

t o t h e i n p u t T h e r a t i o of t h e a m p l i t u d e of t h e o u t p u t s i n u s o i d ( V0) t o t h e a m p l i t u d e o f t h e

i n p u t s i n u s o i d (V-) is t h e m a g n i t u d e of t h e amplifier gain (or t r a n s m i s s i o n ) at t h e test fre­

q u e n c y co A l s o , t h e a n g l e p is t h e p h a s e of t h e a m p l i f i e r t r a n s m i s s i o n a t the test f r e q u e n c y

amplifier is a l m o s t constant, to within a certain n u m b e r of decibels (usually 3 d B ) , is called the

amplifier b a n d w i d t h N o r m a l l y t h e amplifier is d e s i g n e d s o that its b a n d w i d t h c o i n c i d e s

with t h e s p e c t r u m of t h e signals it is r e q u i r e d t o amplify If this w e r e n o t t h e c a s e , t h e a m p l i ­

fier w o u l d distort t h e f r e q u e n c y s p e c t r u m o f t h e i n p u t signal, w i t h different c o m p o n e n t s of

W e n o w briefly d i s c u s s t h e m e t h o d for analytically o b t a i n i n g a n e x p r e s s i o n for t h e fre­

q u e n c y r e s p o n s e W h a t w e a r e a b o u t to say is j u s t a p r e v i e w of this i m p o r t a n t subject, w h o s e detailed study starts i n C h a p t e r 4

T o e v a l u a t e t h e f r e q u e n c y r e s p o n s e of a n amplifier o n e h a s t o a n a l y z e t h e amplifier equivalent circuit m o d e l , t a k i n g i n t o a c c o u n t all r e a c t i v e c o m p o n e n t s 2 Circuit analysis

p r o c e e d s in t h e u s u a l fashion b u t w i t h i n d u c t a n c e s a n d c a p a c i t a n c e s r e p r e s e n t e d b y their

r e a c t a n c e s A n i n d u c t a n c e L h a s a r e a c t a n c e or i m p e d a n c e jcoL, a n d a c a p a c i t a n c e C h a s a

r e a c t a n c e or i m p e d a n c e 1 / jcoC or, e q u i v a l e n t l y , a s u s c e p t a n c e or a d m i t t a n c e jcoC T h u s i n a frequency-domain a n a l y s i s w e d e a l w i t h i m p e d a n c e s a n d / o r a d m i t t a n c e s T h e result of t h e analysis is t h e amplifier transfer function T(co):

T(co) = ^

V,(a»

w h e r e V-ico) a n d V a (co) d e n o t e t h e input a n d o u t p u t s i g n a l s , r e s p e c t i v e l y T(co) is g e n e r a l l y a

c o m p l e x function w h o s e m a g n i t u d e \T(co)\ g i v e s t h e m a g n i t u d e of t r a n s m i s s i o n or t h e m a g ­ nitude r e s p o n s e of t h e amplifier T h e p h a s e of T(co) gives t h e p h a s e r e s p o n s e of t h e amplifier

In t h e a n a l y s i s of a circuit t o d e t e r m i n e its f r e q u e n c y r e s p o n s e , t h e a l g e b r a i c m a n i p u l a ­

tions c a n b e c o n s i d e r a b l y simplified b y u s i n g t h e c o m p l e x f r e q u e n c y v a r i a b l e s I n t e r m s

of s, t h e i m p e d a n c e of an i n d u c t a n c e L is sL a n d that of a c a p a c i t a n c e C i s 1/sC R e p l a c i n g

the r e a c t i v e e l e m e n t s w i t h their i m p e d a n c e s a n d p e r f o r m i n g s t a n d a r d circuit a n a l y s i s , w e

obtain t h e transfer function T(s) as

Vt(s)

S u b s e q u e n t l y , w e r e p l a c e s b y jco to d e t e r m i n e t h e transfer function for p h y s i c a l f r e q u e n ­

cies, T(jco) N o t e that T(jco) is t h e s a m e function w e c a l l e d T(co) a b o v e ;3 t h e a d d i t i o n a l j is

i n c l u d e d in o r d e r t o e m p h a s i z e that T(jco) is o b t a i n e d from T(s) b y r e p l a c i n g s w i t h j co

1.6.4 Single-Time-Constant Networks

In a n a l y z i n g amplifier circuits to d e t e r m i n e their f r e q u e n c y r e s p o n s e , o n e is greatly a i d e d b y

k n o w l e d g e of t h e f r e q u e n c y r e s p o n s e characteristics of s i n g l e - t i m e - c o n s t a n t ( S T C ) n e t w o r k s

A n S T C n e t w o r k is o n e t h a t is c o m p o s e d of, or c a n b e r e d u c e d t o , o n e r e a c t i v e c o m p o n e n t ( i n d u c t a n c e o r c a p a c i t a n c e ) a n d o n e r e s i s t a n c e E x a m p l e s a r e s h o w n i n F i g 1.22 A n S T C

in p a r t i c u l a r t h e f r e q u e n c y r e s p o n s e r e s u l t s ; w e will, in fact, briefly d i s c u s s this i m p o r t a n t

t o p i c , n o w

2 Note that in the models considered in previous sections no reactive components were included These were simplified models and cannot be used alone to predict the amplifier frequency response

3 At this stage, we are using s simply as a shorthand for jco We shall not require detailed knowledge of

i-plane concepts until Chapter 6 A brief review of j-plane analysis is presented in Appendix E

F I G U R E 1 2 2 Two examples of STC networks: (a) a low-pass network and

frequencies) T(jco) 1 +j(co/co 0 ) l-j(co 0 /co)

7 L + (co/co 0 ) 2 Ji + (m g /co) 2 Phase Response ZT(jco) - t a n- 1( co/co 0 ) tan ' ( ( O g / c o )

e x a m p l e , t h e S T C n e t w o r k s h o w n in F i g 1.22(a) is of t h e low-pass t y p e a n d that in F i g 1.22(b)

is of t h e high-pass t y p e T o s e e t h e r e a s o n i n g b e h i n d this classification, o b s e r v e that t h e

transfer function of e a c h of t h e s e t w o circuits c a n b e e x p r e s s e d as a v o l t a g e - d i v i d e r ratio,

4 An important exception is the all-pass STC network studied in Chapter 11

5 A filter is a circuit that passes signals in a specified frequency band (the filter passband) and stops or severely attenuates (filters out) signals in another frequency band (the filter stopband) Filters will be studied in Chapter 12

6 The transfer functions in Table 1.2 are given in general form For the circuits of Fig 1.22, K = 1 and

F I G U R E 1 2 4 (a)Magnitude and (b) phase response of STC networks of the high-pass type

CHAPTER 1 I N T R O D U C T I O N T O E L E C T R O N I C S

T h e s e f r e q u e n c y r e s p o n s e d i a g r a m s a r e k n o w n as B o d e p l o t s and t h e 3- d B f r e q u e n c y (<%)

is also k n o w n as t h e c o r n e r f r e q u e n c y o r b r e a k f r e q u e n c y T h e r e a d e r is u r g e d t o b e c o m e

familiar w i t h this i n f o r m a t i o n a n d t o c o n s u l t A p p e n d i x D if further clarifications are n e e d e d

In particular, it is i m p o r t a n t t o d e v e l o p a facility for t h e r a p i d d e t e r m i n a t i o n of t h e t i m e c o n

-stant T of a n S T C circuit

! ML; are 1.25 shows a voltage amplifier having an input resistance an input capacitance Q , a

IMIN factor ¡1, and an output resistance R 0 T h e amplifier is fed with a voltage source V s having

lurce resistance R s , and a load of resistance R L is connected to the output

j FIGURE 1 2 5 Circuit for Example 1.5

I (a) Derive an expression for the amplifier voltage gain V 0 /V s as a function of frequency F r o m

I this find expressions for the dc gain and the 3-dB frequency

I (b) Calculate t h e values of the dc gain, t h e 3-dB frequency, and t h e frequency at w h i c h t h e

gain b e c o m e s 0 dB (i.e., unity) for the case R s = 2 0 k Q , R, = 100 k Q , C, = 60 pF, ¡1 = 144 V / V ,

where Z t is the amplifier input impedance Since Z; is composed of two parallel elements it is

obviously easier to w o r k in terms of Y- = 1/Z,- Toward that end w e divide the numerator and

denominator by Z,, thus obtaining

This expression can b e put in the standard form for a low-pass S T C network (see the top line of

Table 1.2) by extracting [ 1 + (R/R t )] from the denominator; thus w e have

W e note that only the last factor in this expression is n e w (compared with the expression derived

in the last section) This factor is a result of the input capacitance C;, with the time constant being

T = C s '

= CtiRJ/Ri)

W e could have obtained this result by inspection: F r o m Fig 1.25 w e see that the input circuit is

an STC network and that its time constant can b e found by reducing V s t o zero, with the result that the resistance seen by C; is R, in parallel with R s T h e transfer function in Eq (1.21) is of the form K/( 1 + (s/c O q)), which corresponds to a low-pass S T C network T h e dc gain is found as

The 3-dB frequency CO 0 can b e found from

Since the frequency response of this amplifier is of the low-pass S T C type, the B o d e plots for the

gain magnitude and phase will take the form shown in Fig 1.23, where K is given b y Eq (1.23) and a> 0 is given b y Eq (1.24)

(b) Substituting the numerical values given into Eq (1.23) results in

1 + ( 2 0 / 1 0 0 ) 1 + ( 2 0 0 / 1 0 0 0 ) Thus the amplifier has a dc gain of 40 d B Substituting the numerical values into Eq (1.24) gives the 3-dB frequency

1

0 6 0 p F x (20 k ß / / 1 0 0 k Q )

60 x 1 0 ~1 2 x (20 x 1 0 0 / ( 2 0 + 100)) x 1 03 Thus,

/0 = = 159.2 k H z

Since the gain falls off at the rate of - 2 0 dB/decade, starting at CO 0 (see Fig 1.23a) the gain will

reach 0 dB in t w o decades (a factor of 100); thus w e have

Unity-gain frequency = 1 0 0 x c o0 = 1 08 rad/s or 15.92 M H z

(c) T o find v 0 (t) w e need to determine the gain magnitude and phase at 1 02, 1 05, 1 06, and 1 08 rad/s

This can b e done either approximately utilizing the B o d e plots of Fig 1.23 or exactly utilizing

the expression for the amplifier transfer function,

T(jio)^(jco) = 100

vs 1 + 7 ( o / 1 0 )

W e shall do both:

(i) For co= 1 02 rad/s, which is ( f t )0/ 1 04) , the B o d e plots of Fig 1.23 suggest that 171 = K= 100

and 0 = 0 ° T h e transfer function expression gives i n = 100 and <j) = - t a n- 1 1 0- 4 = 0° Thus,

v 0 (t) = 10 sin \0 2 t, V

(ii) For CO = 1 05 rad/s, which is ( f f l0/ 1 0 ) , the B o d e plots of Fig 1.23 suggest that \T\-K= 100

and <p = -5.7° T h e transfer function expression gives i n = 99.5 and 0 = - t a n- 1 0.1 = - 5 7 ° Thus,

v a (t) = 9.95 s i n ( 1 05f - 5 7 ° ) , V

(iii) For CO = 1 06 rad/s = co 0 , \T\ = 100/72 = 70.7 V/V or 37 dB and cj> = - 4 5 ° Thus,

wo(/) = 7.07 s i n ( 1 06f - 4 5 ° ) , V

(iv) For CO = 1 08 rad/s, which is ( 1 0 0 o0) , the B o d e plots suggest that i n = 1 and (j) = - 9 0 ° T h e

transfer function expression gives

LTI = 1 and cj) = - t a n "1 100 = - 8 9 4 ° , Thus,

v o (t) = 0.l s i n ( 1 08r - 8 9 4 ° ) , V

1.6.5 Classification of Amplifiers Based on Frequency Response

Amplifiers can b e classified b a s e d on the shape of their m a g n i t u d e - r e s p o n s e curve Figure 1.26

s h o w s t y p i c a l f r e q u e n c y r e s p o n s e c u r v e s for v a r i o u s amplifier t y p e s In F i g 1.26(a) t h e g a i n

r e m a i n s c o n s t a n t o v e r a w i d e frequency r a n g e b u t falls off at l o w and h i g h f r e q u e n c i e s T h i s

is a c o m m o n t y p e of f r e q u e n c y r e s p o n s e f o u n d in a u d i o amplifiers

A s will b e s h o w n in later chapters, internal c a p a c i t a n c e s in the device (a transistor) cause

the falloff of gain at high frequencies, j u s t as C t did in the circuit of E x a m p l e 1.5 O n t h e other

hand, the falloff of gain at l o w frequencies is usually c a u s e d b y c o u p l i n g capacitors u s e d to

connect o n e amplifier stage to another, as indicated in Fig 1.27 This practice is usually adopted

to simplify t h e design process of the different stages T h e coupling capacitors are usually c h o ­

sen quite large (a fraction of a microfarad to a few tens of microfarads) so that their reactance

(impedance) is small at t h e frequencies of interest Nevertheless, at sufficiently low frequencies

the reactance of a coupling capacitor will b e c o m e large e n o u g h to cause part of the signal being

c o u p l e d to a p p e a r as a v o l t a g e d r o p across t h e c o u p l i n g c a p a c i t o r a n d t h u s n o t r e a c h t h e s u b ­

s e q u e n t stage C o u p l i n g capacitors will thus c a u s e loss of gain at l o w frequencies a n d c a u s e

the gain to b e zero at d c This is not at all surprising since from Fig 1.27 w e observe that the

coupling capacitor, acting together with the input resistance of the subsequent stage, forms a

1.6 F R E Q U E N C Y R E S P O N S E O F A M P L I F I E R S ! 3 9

Center frequency to (c)

F I G U R E 1 2 6 Frequency response for (a) a capacitively coupled amplifier, (b) a direct-coupled amplifier,

and (c) a tuned or bandpass amplifier

Two amplifier stages

t h e c e n t e r f r e q u e n c y ) a n d falls off on b o t h sides of this f r e q u e n c y , as s h o w n in F i g 1.26(c)

fSJf.21rf@onsider a voltage amplifier h a v i n g a frequency r e s p o n s e of the l o w - p a s s S T C t y p e with a dc gain

of 6 0 dB and a 3-dB frequency of 1000 H z Find the gain in d B a t / = 10 H z , 10 k H z , 100 k H z , and

Ans.MnlH:4l><IB: : n , l | }; u J H

DiJi22»<@omsider a transconductance amplifier having the model shown in Table 1.1 with R ; = 5 k Q R u = 50 k Q ,

mm: s a n d G,„ = 10 m A / V If the amplifier load consists of a resistance R L in parallel with a capacitance C L

convince yourself that the voltage transfer function realized, VJV t is of the low-pass S T C type W h a t is

the lowest value that R L can have while a dc gain of at least 4 0 dB is obtained? With this value of R L

connected, find the highest value that C L can h a v e while a 3-dB b a n d w i d t h of at least 100 k H z is

obtained

Ans. 1 2 5 k Q ; 159.2 p F

D1.23 Consider the situation illustrated in Fig 1.27 Let the output resistance of the first v o l t a g e amplifier b e

1 k Q a n d the input resistance of the second voltage amplifier (including the resistor shown) be 9 k Q

T h e resulting equivalent circuit is shown in Fig E 1 2 3 where % and R s are the output voltage and out­

put resistance of the first amplifier, C is a coupling capacitor, a n d J ?; is the input resistance of the second

amplifier Convince y o u r s e l f that V 2 /V s is a high-pass S T C function W h a t is ;the smallest value for C

that will ensure that t h e 3-dB frequency is not higher t h a n 100 H z ?

— — F I G U R E E 1 2 3

Ans. 0 1 6 , u l '

«««;•« >.:::>s

T h e logic inverter is the m o s t basic e l e m e n t in digital circuit design; it plays a role parallel to that

of the amplifier in analog circuits In this section w e p r o v i d e an introduction to the logic inverter

1.7.1 Function of the Inverter

A s its n a m e i m p l i e s , t h e l o g i c i n v e r t e r i n v e r t s t h e logic v a l u e of its i n p u t signal T h u s for a

1.7.2 The Voltage Transfer Characteristic (VTC)

T o quantify t h e o p e r a t i o n of t h e inverter, w e utilize its v o l t a g e transfer c h a r a c t e r i s t i c ( V T C ,

as it is usually abbreviated) First w e refer t h e r e a d e r to the amplifier considered in E x a m p l e 1.2

w h o s e transfer c h a r a c t e r i s t i c is s k e t c h e d in F i g 1.15 O b s e r v e that t h e transfer c h a r a c t e r i s t i c indicates t h a t this i n v e r t i n g amplifier c a n b e u s e d as a l o g i c inverter Specifically, if t h e

input is h i g h (V[ > 0 6 9 0 V ) , v Q w i l l b e l o w at 0.3 V O n t h e o t h e r h a n d , if t h e input is l o w (close to 0 V ) , t h e o u t p u t will b e h i g h (close t o 10 V ) T h u s t o u s e this a m p l i f i e r as a l o g i c inverter, w e u t i l i z e its e x t r e m e r e g i o n s of o p e r a t i o n T h i s is e x a c t l y t h e o p p o s i t e to its u s e as

a signal amplifier, w h e r e it w o u l d b e b i a s e d at the m i d d l e of the transfer c h a r a c t e r i s t i c a n d the signal k e p t sufficiently s m a l l so as t o restrict o p e r a t i o n t o a short, a l m o s t linear, s e g m e n t

of t h e t r a n s f e r c u r v e D i g i t a l a p p l i c a t i o n s , o n t h e o t h e r h a n d , m a k e u s e of t h e g r o s s n o n linearity e x h i b i t e d b y t h e V T C

-W i t h t h e s e o b s e r v a t i o n s i n m i n d , w e s h o w in F i g 1.29 a p o s s i b l e V T C of a l o g i c inverter F o r s i m p l i c i t y , w e a r e u s i n g t h r e e straight lines to a p p r o x i m a t e the V T C , w h i c h is usually a n o n l i n e a r c u r v e s u c h as that in F i g 1.15 O b s e r v e t h a t t h e o u t p u t h i g h level,

% A

FIGURE 1 2 9 Voltage transfer characteristic of an inverter The VTC is approximated by three

straight-line segments Note the four parameters of the VTC (V 0H , V 0L , V 1L , and V m ) and their use in determining the

noise margins (NM H and NM L )

A m p l i f i e r s w i t h s u c h a r e s p o n s e are called t u n e d a m p l i f i e r s , b a n d p a s s a m p l i f i e r s , o r

b a n d p a s s filters A t u n e d a m p l i f i e r f o r m s t h e h e a r t of t h e f r o n t - e n d or t u n e r of a c o m m u n i ­

c a t i o n r e c e i v e r ; b y adjusting its c e n t e r f r e q u e n c y t o c o i n c i d e w i t h t h e f r e q u e n c y of a d e s i r e d

c o m m u n i c a t i o n s c h a n n e l (e.g., a r a d i o station), t h e signal of this p a r t i c u l a r c h a n n e l c a n b e

r e c e i v e d w h i l e t h o s e of o t h e r c h a n n e l s are a t t e n u a t e d or filtered out

d e n o t e d V 0H , d o e s n o t d e p e n d o n t h e e x a c t v a l u e of vj as l o n g a s v 1 d o e s n o t e x c e e d t h e v a l u e

l a b e l e d V IL ; w h e n Vj e x c e e d s V 1L , t h e o u t p u t d e c r e a s e s a n d t h e i n v e r t e r enters its amplifier

r e g i o n of o p e r a t i o n , a l s o called t h e t r a n s i t i o n r e g i o n It f o l l o w s that V IL is an i m p o r t a n t

p a r a m e t e r of t h e i n v e r t e r V T C : I t is t h e maximum value that v l can have while being inter­

preted by the inverter as representing a logic 0

S i m i l a r l y , w e o b s e r v e that t h e o u t p u t l o w level, d e n o t e d V 0L , d o e s n o t d e p e n d o n t h e

e x a c t v a l u e of Vj as l o n g as v 1 d o e s n o t fall b e l o w V IH T h u s V IH is a n i m p o r t a n t p a r a m e t e r of

t h e i n v e r t e r V T C : I t is t h e minimum value that Vj can have while being interpreted by the

inverter as representing a logic 1

1.7.3 Noise Margins

T h e i n s e n s i t i v i t y of t h e i n v e r t e r o u t p u t t o t h e e x a c t v a l u e of vj w i t h i n a l l o w e d r e g i o n s is a

g r e a t a d v a n t a g e t h a t digital circuits h a v e o v e r a n a l o g circuits T o quantify this insensitivity

p r o p e r t y , c o n s i d e r t h e situation t h a t o c c u r s often in a digital s y s t e m w h e r e a n i n v e r t e r (or a

d e t e r m i n e its n o i s e m a r g i n s , w h i c h in t u r n m e a s u r e t h e ability of t h e inverter to t o l e r a t e vari­

ations i n t h e i n p u t signal l e v e l s I n this r e g a r d , o b s e r v e that c h a n g e s i n t h e i n p u t s i g n a l l e v e l

TABL.fc 1.3 important Parameters of the VTC of the Logic Inverter (Refer to Fig 1.29)

V 0L : Output low level

V 0H : Output high level

V 1L : Maximum value of input interpreted by the inverter as a logic 0

V lH : Minimum value of input interpreted by the inverter as a logic 1

NM L : Noise margin for low input = V IL - V 0L

NM H : Noise margin for high input = V 0H - V m

1.7.4 The Ideal VTC

T h e q u e s t i o n n a t u r a l l y arises as t o w h a t c o n s t i t u t e s a n ideal V T C for a n inverter T h e a n s w e r follows directly f r o m t h e p r e c e d i n g d i s c u s s i o n : A n i d e a l V T C is o n e t h a t m a x i m i z e s t h e noise m a r g i n s a n d distributes t h e m e q u a l l y b e t w e e n t h e l o w a n d h i g h i n p u t r e g i o n s S u c h a

T h e transition r e g i o n , t h o u g h o b v i o u s l y v e r y i m p o r t a n t for amplifier a p p l i c a t i o n s , is of n o

v a l u e in digital circuits T h e i d e a l V T C e x h i b i t s a steep transition at t h e t h r e s h o l d v o l t a g e

A A

v 0

(a)

f/ low (b)

F I G U R E 1.31 (a) The simplest implementation of a logic inverter using a voltage-controlled switch;

(b) equivalent circuit when v, is low; and (c) equivalent circuit when v, is high Note that the switch is

assumed to close when v, is high

an o p e n circuit, the " o n " s w i t c h has a finite c l o s u r e o r " o n " r e s i s t a n c e , R on F u r t h e r m o r e ,

F I G U R E 1 3 2 A more elaborate implementation of the logic inverter utilizing two complementary

switches This is the basis of the CMOS inverter studied in Section 4.10

in the e q u i v a l e n t circuit s h o w n in Fig 1.32(c) H e r e R m of the P D s w i t c h c o n n e c t s the o u t p u t

to g r o u n d , t h u s e s t a b l i s h i n g V 0L = 0 H e r e a g a i n n o c u r r e n t f l o w s , a n d n o p o w e r is dissi­

p a t e d T h e s u p e r i o r i t y of this i m p l e m e n t a t i o n o v e r that u s i n g t h e single p u l l - d o w n s w i t c h and a resistor ( k n o w n as a p u l l - u p resistor) s h o u l d b e o b v i o u s T h i s circuit constitutes t h e basis

of t h e C M O S i n v e r t e r t h a t w e will study in S e c t i o n 4 1 0 N o t e that w e h a v e n o t i n c l u d e d off­

set v o l t a g e s in t h e e q u i v a l e n t circuits b e c a u s e M O S s w i t c h e s d o n o t e x h i b i t a v o l t a g e offset ( C h a p t e r 4 )

e q u a t i o n i n d e t e r m i n i n g t h e r e s p o n s e t o a step function:

C o n s i d e r a stepfunction i n p u t a p p l i e d t o a n S T C n e t w o r k of e i t h e r t h e l o w p a s s o r h i g h

-p a s s t y -p e , a n d l e t t h e n e t w o r k h a v e a t i m e c o n s t a n t T T h e o u t -p u t at a n y t i m e t is g i v e n b y

w h e r e Y„ i s t h e final v a l u e , t h a t is, t h e v a l u e t o w a r d w h i c h t h e r e s p o n s e is h e a d i n g , a n d F0 +

is t h e v a l u e of t h e r e s p o n s e i m m e d i a t e l y after t = 0 T h i s e q u a t i o n s t a t e s t h a t t h e o u t p u t at

a n y t i m e t i s e q u a l t o t h e difference b e t w e e n t h e final v a l u e Y„ a n d a g a p w h o s e initial v a l u e

is F „ - 70 + a n d t h a t i s s h r i n k i n g e x p o n e n t i a l l y

( msider the inverter of Fig 1.31(a) with a capacitor C = 10 p F connected between the output

I ground L e t V DD = 5 V , R = 1 k Q , R on = 100 Q , and V oSset = 0.1 V If at t = 0, Vj goes low a n d

n c d e c t i n g the delay time of the switch, that is, assuming that it opens immediately, find the time the output t o reach l(V 0H + V 0L ) T h e time t o this 5 0 % point on the output waveform is

m e d as the low-to-high propagation delay, t P L H

S o l u t i o n

First w e d e t e r m i n e V 0L , w h i c h is the voltage at t h e output prior to t = 0 F r o m the equivalent

circuit in Fig 1.31(b), w e find

Next when the switch opens at t = 0, the circuit takes t h e form shown in Fig 1.34(a) Since the

voltage across the capacitor cannot change instantaneously, at t = 0 + the output will still b e 0.55 V

F I G U R E 1.34 Example 1.6: (a) The inverter circuit after the switch opens (i.e., for t>0+). (b) Waveforms

of v, and v 0 Observe that the switch is assumed to operate instantaneously v 0 rises exponentially, starting at

V 0L and heading toward V 0H

Then the capacitor charges through R, a n d v 0 rises exponentially toward V DD T h e output w a v e ­

form will b e as shown in F i g 1.34(b), and its equation can b e obtained b y substituting in

1.24 For the inverter in Fig 1.31, let V DD = 5 V, R = 1 kí2, R u „ = 100 Q , V oifia = 0.1 V V, L = 0.8 V, and V IH =1.2 V

Find V 0H , V 0L , NM H , and NM,, Also find lhe average static power dissipation assuming that lhe inverter

spends half the time in each of its two stales

A n s 5 \ ' : ( i 5 5 V : 3 s V : i > : 5 \ : I 1.1m\ \

1.25 Find the dynamic power dissipated in an inverter operated from a 5-V power supply The inverter has a

2-pF capacitance load and is switched at 50 M H z

Ans. 2.5 mW

1.8 CIRCUIT SIMULATION USING SPICE

T h e u s e of c o m p u t e r p r o g r a m s t o simulate t h e operation of electronic circuits h a s b e c o m e a n essential step i n t h e circuit-design p r o c e s s T h i s is especially t h e c a s e for circuits that are t o

b e fabricated i n integrated-circuit form H o w e v e r , e v e n circuits that a r e a s s e m b l e d o n a printed-circuit b o a r d u s i n g discrete c o m p o n e n t s can a n d d o benefit from circuit simulation

Circuit simulation e n a b l e s t h e d e s i g n e r to verify that t h e design will m e e t specifications w h e n actual c o m p o n e n t s (with their m a n y imperfections) a r e used, a n d it c a n also p r o v i d e addi­

tional insight into circuit operation allowing the designer t o fine-tune t h e final design prior t o fabrication H o w e v e r , n o t w i t h s t a n d i n g t h e a d v a n t a g e s of c o m p u t e r simulation, it is not a s u b ­stitute for a t h o r o u g h u n d e r s t a n d i n g of circuit operation It s h o u l d b e p e r f o r m e d only a t a later stage i n the design p r o c e s s and, m o s t certainly, after a p a p e r - a n d - p e n c i l d e s i g n has b e e n d o n e

A m o n g t h e v a r i o u s c i r c u i t - s i m u l a t i o n p r o g r a m s a v a i l a b l e for t h e c o m p u t e r - a i d e d n u m e r ­

ical analysis of m i c r o e l e c t r o n i c circuits, S P I C E (Simulation P r o g r a m w i t h i n t e g r a t e d Cir­

cuit Emphasis) i s g e n e r a l l y r e g a r d e d t o b e t h e m o s t w i d e l y used; S P I C E i s a n o p e n - s o u r c e

T h e u s e r h a d t o d e s c r i b e t h e circuit t o b e simulated a n d t h e t y p e of s i m u l a t i o n t o b e per­

formed u s i n g a n i n p u t text file, called a netlist T h e s i m u l a t i o n results w e r e also d i s p l a y e d

as text A s an e x a m p l e of m o r e r e c e n t d e v e l o p m e n t s , C a d e n c e p r o v i d e s a g r a p h i c a l inter­

face, called O r C A D C a p t u r e C I S ( C o m p o n e n t i n f o r m a t i o n S y s t e m ) , for c i r c u i t - s c h e m a t i c entry a n d editing S u c h g r a p h i c a l interface t o o l s are referred t o in the literature as s c h e m a t i c entry, s c h e m a t i c e d i t o r , o r s c h e m a t i c c a p t u r e tools F u r t h e r m o r e , P S p i c e A / D i n c l u d e s a graphical p o s t p r o c e s s o r , called P r o b e , t o n u m e r i c a l l y a n a l y z e a n d graphically d i s p l a y t h e results of t h e P S p i c e s i m u l a t i o n s I n this text, " u s i n g P S p i c e " o r " u s i n g S P I C E " l o o s e l y

refers t o u s i n g C a p t u r e C I S , P S p i c e A / D , a n d P r o b e t o s i m u l a t e a circuit a n d t o n u m e r i c a l l y analyze a n d g r a p h i c a l l y d i s p l a y t h e s i m u l a t i o n r e s u l t s

A n evaluation (student) version of Capture CIS and PSpice A / D are included o n t h e C D accompanying this book T h e s e correspond to the O r C A D Family Release 9.2 Lite Edition avail­

able from Cadence Furthermore, the circuit diagrams entered in Capture CIS (called C a p t u r e Schematics) and the corresponding P S p i c e simulation Files of all S P I C E e x a m p l e s i n this b o o k

can b e found on t h e t e x t ' s C D and website (www.sedrasmith.org) Access t o these files will allow the reader to undertake further experimentation with these circuits, including investigating the effect of changing c o m p o n e n t values and operating conditions

It is n o t o u r o b j e c t i v e in this b o o k t o t e a c h t h e r e a d e r how S P I C E w o r k s n o r t h e intri­

cacies of u s i n g it effectively T h i s c a n b e f o u n d i n t h e S P I C E b o o k s listed i n A p p e n d i x F

O u r objective i n t h e sections of this b o o k d e v o t e d t o S P I C E , u s u a l l y t h e last section of e a c h chapter, i s t w o f o l d : t o d e s c r i b e t h e m o d e l s that are u s e d b y S P I C E t o r e p r e s e n t t h e v a r i o u s electronic d e v i c e s , a n d t o illustrate h o w useful S P I C E c a n b e i n i n v e s t i g a t i n g circuit operation

Such circuits are called mixed-signal circuits, and the simulation programs that can simulate such circuits are called mixed-signal simulators

5 0 ¿ ¿ ' j CHAPTER 1 I N T R O D U C T I O N T O E L E C T R O N I C S

• An electrical signal source can be represented in either the

Thevenin form (a voltage source v s in series with a source

resistance R s ) or the Norton form (a current source i s in

parallel with a source resistance The Thevenin voltage

v s is the open-circuit voltage between the source terminals;

equal to the Norton current i s is equal to the short-circuit

current between the source tenrrinals For the two

represen-tations to be equivalent, v s - R s i s

m The sine-wave signal is completely characterized by its

peak value (or rms value which is the p e a k / J2), its

fre-quency (coin, rad/s o r / i n Hz; co= 2nfaaAf= l/T where

T i s the period in seconds), and its phase with respect to

an arbitrary reference time

• A signal can be represented either by its waveform versus

time, or as the sum of sinusoids The latter representation

is known as the frequency spectrum of the signal

• Analog signals have magnitudes that can assume any

value Electronic circuits that process analog signals are

called analog circuits Sampling the magnitude of an

ana-log signal at discrete instants of time and representing

each signal sample by a number, results in a digital signal

Digital signals are processed by digital circuits

K The simplest digital signals are obtained when the binary

system is used An individual digital signal then assumes

one of only two possible values: low and high (say, 0 V and

+5 V), corresponding to logic 0 and logic 1, respectively

M An analog-to-digital converter (ADC) provides at its

out-put the digits of the binary number representing the

ana-log signal sample applied to its input The output digital

signal can then be processed using digital circuits Refer

to Fig 1.9 and Eq 1.3

• The transfer characteristic, v 0 versus v h of a linear

ampli-fier is a straight line with a slope equal to the voltage gain

Refer to Fig 1.11

• Amplifiers increase the signal power and thus require dc

power supplies for their operation

H The amplifier voltage gain can be expressed as a ratio

A v in V/V or in decibels, 20 log\AJ, dB Similarly, for

cur-rent gain: A t A/A or 20 logL4,l, dB For power gain: A p

W / W o r l O l o g A ^ d B

• Linear amplification can be obtained from a device

hav-ing a nonlinear transfer characteristic by employhav-ing dc

biasing and keeping the input signal amplitude small Refer

to Fig 1.14

• Depending on the signal to be amplified (voltage or

cur-rent) and on the desired form of output signal (voltage or

current), there are four basic amplifier types: voltage, current, transconductance, and transresistance amplifiers

For the circuit models and ideal characteristics of these four amplifier types, refer to Table 1.1 A given amplifier can be modeled by any one of the four models, in which case their parameters are related by the formulas in Eqs (1.14) to (1.16)

H A sinusoid is the only signal whose wave form is changed through a linear circuit Sinusoidal signals are used to measure the frequency response of amplifiers

un-• The transfer function T(s) = V 0 (s)/V-(s) of a voltage

amplifier can be determined from circuit analysis

Substi-tuting s = jco gives T(jco), whose magnitude \T(jco)\ is the magnitude response, and whose phase (p(co) is the phase

response, of the amplifier

• Amplifiers are classified according to the shape of their

frequency response, \T(jm)\ Refer to Fig 1.26

• Single-time-constant (STC) networks are those networks that are composed of, or can be reduced to, one reactive

component (L or Q and one resistance (R) The time stant T is either L/R or CR

con-• STC networks Can be classified into two categories: pass (LP) and high-pass (HP) LP networks pass dc and low frequencies and attenuate high frequencies The op-posite is true for HP networks

low-B The gain of an LP (HP) STC circuit drops by 3 dlow-B below the zero-frequency (infinite-frequency) value at a fre-

quency C0g = Hi. At high frequencies (low frequencies) the gain falls off at the rate of 6 dB/octave or 20 dB/decade

Refer to Table 1.2 on page 34 and Figs (1.23) and (1.24)

Further details are given in Appendix E

• The digital logic inverter is the basic building block of digital circuits, just as the amplifier is the basic building block of analog circuits

• The static operation of the inverter is described by its age transfer characteristic (VTC) The break-points of the transfer characteristic determine the inverter noise mar-gins; refer to Fig 1.29 and Table 1.3 In particular, note

volt-that NM H = V 0H - V m and NM L = V IL - V 0L

• The inverter is implemented using transistors operating as voltage-controlled switches The arrangement utilizing two switches operated in a complementary fashion results

in a high-performance inverter This is the basis for the CMOS inverter studied in Chapter 4

• An important performance parameter of the inverter is the amount of power it dissipates There are two components of power dissipation: static and dynamic The first is a result

of current flow in either the 0 or 1 state or both The second

R E S I S T O R S A N D O H M ' S L A W

1 1 Ohm's law relates V, I, and R for a resistor For each of

the situations following, find the missing item:

(a) i? = l k Q , V = 1 0 V

(b) V= 10V,7 = 1 m A

(c) fl=10kQ,/=10mA

1 2 Measurements taken on various resistors are shown below

For each, calculate the power dissipated in the resistor and the power rating necessary for safe operation using standard compo-nents with power ratings of 1/8 W, 1/4 W, 1/2 W, 1 W, or 2 W:

(a) 1 kQ conducting 30 mA (b) 1 kQ conducting 40 mA (c) 10 kQ conducting 3 m A (d) 10 kQ conducting 4 m A (e) 1 kQ dropping 20 V (f) l k Q dropping 11 V

1.3 Ohm's law and the power law for a resistor relate V, I,

R, and P, making only two variables independent For each

pair identified below, find the other two:

(a) R= 1 k Q , / = 10 mA

(b) V = 1 0 V , / = l m A (c) V = 1 0 V , P = 1 W

(d) 1= 1 0 m A , P = 0.1 W

(e) fl=lkQ,P=lW

C O M B I N I N G R E S I S T O R S

1 4 You are given three resistors whose values are 10 kQ,

20 kQ, and 40 kQ How many different resistances can you

create using series and parallel combinations of these three? List them in value order, lowest first Be thorough and

organized (Hint: In your search, first consider all parallel

combinations, then consider series combinations, and then consider series-parallel combinations, of which there are two kinds)

1 5 In the analysis and test of electronic circuits, it is often useful to connect one resistor in parallel with another to obtain a nonstandard value, one which is smaller than the smaller of the two resistors Often, particularly during circuit testing, one resistor is already installed, in which case the sec-ond, when connected in parallel, is said to "shunt" the first If the original resistor is 10 kQ, what is the value of the shunting resistor needed to reduce the combined value by 1%, 5%, 10%, and 50%? What is the result of shunting a 10-kQ resistor

by 1 M Q ? By 100 kQ? By 10 kQ?

V O L T A G E D I V I D E R S

1 6 Figure PI.6(a) shows a two-resistor voltage divider Its

function is to generate a voltage V 0 (smaller than the

power-supply voltage V DD ) at its output node X The circuit looking

back at node X is equivalent to that shown in Fig PI.6(b) Observe that this is the Thevenin equivalent of the voltage

divider circuit Find expressions for V 0 and R 0